GRID CODE – RULES FOR ELECTRICAL TRANSMISSION SYSTEM OPERATION Macedonian Electrical Transmission System

GRID CODE – RULES FOR
ELECTRICAL TRANSMISSION
SYSTEM OPERATION

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CONTENT
CONTENT............................................................................................................... I
I GENERAL PROVISIONS ...................................................................................1
I.1 Subject of the regulation................................................................................ 1
I.2 Basic principles............................................................................................... 2
I.3. Area of Implementation...................................................................................... 2
I.4 Basic Requirements and Responsibilities ensuing from the Compliance
with the Code .................................................................................................. 3
General Obligations................................................................................................................3
Committee for monitoring and implementation of the Code .................................3
Amendments to the Code and its Interpretation........................................................4
Unforeseen Events and Reporting....................................................................................4
Information and Data Confidentiality.............................................................................5
I.5. Terms, Abbreviations and Definitions................................................................. 5
Terms 5
Definitions 5
Abbreviations 11
II TRANSMISSION SYSTEM DEVELOPMENT PLANNING...................................13
II.1 Scope and Objectives ....................................................................................... 13
Planning-related Activities................................................................................................13
Planning-related Rights and Obligations of TSO.......................................................13
Planning Concept..................................................................................................................14
II.2. Input and Basic Data....................................................................................... 14
General requirements..........................................................................................................14
EE and Power Demand Forecast for users...................................................................15
Data from EE producers......................................................................................................15
Forecast of EE and Power Balance..................................................................................16
Harmonization of Development Plans with Transmission System Users.........16
II.3. Models and Scenarios...................................................................................... 17
Market model 17
Network model ......................................................................................................................17
National model.......................................................................................................................18
Regional model......................................................................................................................18
Planning scenarios................................................................................................................18
II.4 Technical analyses and criteria for planning.................................................... 18
II.4.1 Technical analyses 18
N-1 Security Rule..................................................................................................................19
Market Analyses ....................................................................................................................19
Network Analyses.................................................................................................................20

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Load Flow Analyses..............................................................................................................20
Grid Transfer Capability Analyses...................................................................................20
Optimal Power Flow Analyses..........................................................................................20
Short-circuit Analyses .........................................................................................................21
Voltage Stability Analyses .................................................................................................21
Dynamic Stability Analyses ...............................................................................................21
Reliability Analyses ..............................................................................................................21
II.4.2 Technical criteria for network parameters assessment........................................................22
Steady state criteria.............................................................................................................22
Maximum loss of load/generation criteria..................................................................22
Short circuit criteria.............................................................................................................22
Voltage stability criteria.....................................................................................................22
Dynamic stability criteria...................................................................................................22
II.5. Solution proposals........................................................................................... 23
II.6. Project Assessment......................................................................................... 24
General .......................................................................................................................24
Project .......................................................................................................................24
Interconnection Project .....................................................................................................25
Benefit Categories ................................................................................................................25
Project costs .......................................................................................................................25
Social and Enviromental Impact .....................................................................................26
Spatial Planning Criteria ....................................................................................................26
Environmental and Technical Needs for System Rationalization........................26
Sensitivity Analysis...............................................................................................................26
II.7. Transmission Development Study................................................................... 26
General .......................................................................................................................26
Methodology .......................................................................................................................27
Integration of Study in Pan-European and Regional Plans...................................27
II.8. Preparation of Plan ......................................................................................... 27
Strategic plan for transmission system........................................................................27
Development plan for EPS.................................................................................................28
Investment plan for transmission system...................................................................28
II.9. Implementation .............................................................................................. 28
Solutions implementation..................................................................................................28
II.10. Evaluation of transmission network adequacy (ENTSO-E SAF)..................... 29
Criteria .......................................................................................................................29
Report form .......................................................................................................................29
III TRANSMISSION SYSTEM CONNECTION REQUIREMENTS............................30
III.1 General......................................................................................................... 30
III.2 Objectives...................................................................................................... 30
III.3 Connection Procedure .................................................................................. 30

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Procedure for connection to the transmission network.........................................30
Documents for the procedure...........................................................................................31
Application for approval to connect to the transmission network .....................31
Study of connection to the transmission network....................................................31
Harmonization of the technical solution of the Study for connection between
TSO and the applicant ...........................................................................32
Decision for approval of the connection to the transmission network.............33
Contract for connection to the transmission network............................................33
Approval of project documentation ...............................................................................34
Reporting for the process of connection of the infrastructure of a user to
transmission network............................................................................34
Agreement for use of the transmission network ......................................................35
Connection costs...................................................................................................................35
Construction costs for the connection or upgrade (expansion) of an existing
connection .................................................................................................36
Participation in creation of technical conditions in the transmission system
for connection of new customers or increasing the capacity of
existing connections..............................................................................36
Connection infrastructure..................................................................................................36
Change in technical parameters of an existing connection ..................................37
III.4 General requirements for connection to the transmission system ............... 37
N-1 security criterion...........................................................................................................37
Reactive Power......................................................................................................................37
Facility Control.......................................................................................................................37
Operation in case of faults.................................................................................................37
Power quality .......................................................................................................................38
Frequency and voltages......................................................................................................39
Conditions for short circuits currents and treatment of neutral point .............39
Maintenance .......................................................................................................................40
Protection in the transmission system .........................................................................40
Communication and exchange of data in real time..................................................41
Measurement equipment...................................................................................................42
Procedures for system management.............................................................................43
III.5 Additional requirements for connection to the transmission network ......... 43
III.6 General Compliance...................................................................................... 43
Obligations (responsibilities) of TSO.............................................................................43
Responsibility of the user of the transmission network.........................................44
Common regulation of compliance testing..................................................................44
Common regulation for simulations of compliance .................................................45
Tests for compliance............................................................................................................45
III.7 Exceptions .................................................................................................... 46
General provisions................................................................................................................46
Request for exception.........................................................................................................46

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Decision on exception .........................................................................................................46
IV ELECTRICITY METERING ..............................................................................48
IV.1. Introduction ................................................................................................... 48
IV.2. Objectives and areas of application................................................................ 48
IV.3. Metering point and Electricity Delivery/Withdrawal Point............................ 49
IV.3.1 Definitions and general requirements.................................................................................49
IV.3.2 Metering points location.....................................................................................................50
IV.4. Metering equipment ...................................................................................... 52
IV.4.1 Composing parts of the metering equipment ......................................................................52
IV.4.2 Metering transformers ........................................................................................................52
IV.4.3 Electricity metering devices................................................................................................54
IV.4.4 Signalization and supervision.............................................................................................55
IV.4.5 Communication ...........................................................................................................56
IV.5. Procurement, installation and putting into operation and un-mounting
of the metering equipment............................................................................ 56
IV.6. Parameterization of the metering equipment ................................................ 57
IV.7. Inspection and controlling of the metering devices ...................................... 58
IV.7.1 Introduction ...........................................................................................................58
IV.7.2 Inspections of the metering devices performed by TSO......................................................58
IV.7.3 Inspections of the metering devices by Metrology office ....................................................59
IV.7.4 Metering device testing.......................................................................................................59
IV.8. Access, protection and maintenance of the metering equipment ................. 60
IV.8.1 Access and protection of the metering equipment.......................................60
IV.8.2 Maintenance of the metering equipment .........................................................60
IV.9. Irregular functioning and repairs in the metering system ............................ 61
IV.9.1 Controlling and supervision of the metering ......................................................................61
IV.9.2 Repairs in the metering system ...........................................................................62
IV.10. Metering data ............................................................................................... 62
IV.11.The usage of the metering data .................................................................... 63
IV.12.Processing the metering data........................................................................ 63
IV.12.1 Metering database..................................................................................................63
IV.12.2 Metering data acquisition ....................................................................................64
IV.12.3 Data validation ...........................................................................................................65
IV.12.4 Substitution of data................................................................................................65
IV.12.5 Access to metering data .......................................................................................66
V POWER SYSTEM OPERATION........................................................................68
V.1 Planning of Power System Operation........................................................... 68
V.1.1 Introduction ...........................................................................................................68
V.1.2 Operation Planning Objectives............................................................................................68
V.1.3 General characteristics of plans for EPS operation ............................................................68

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V.1.4 Annually, monthly, weekly and daily plans of EPS operation..............................................69
V.1.5 Disconnection plans in the transmission system ..................................................................72
V.1.6 Security analysis ...........................................................................................................75
V.1.7 Annual, monthly and weekly plans for cross-border transfer capacities.............................76
V.2 System services............................................................................................ 78
V.2.1 Introduction ...........................................................................................................78
V.2.2 Objectives ...........................................................................................................79
V.2.3 General provisions ...........................................................................................................79
V.2.4 Regulation of frequency and power......................................................................................79
V.2.5 Regulation of voltage and reactive power............................................................................83
V.2.6 System restoration after blackout.........................................................................................85
V.3 Power System Control................................................................................... 86
V.3.1 Introduction ...........................................................................................................86
V.3.2 Objectives ...........................................................................................................86
V.3.3 Control under normal operating condition..........................................................................86
Supervision of power system operation.......................................................................87
Intra-day Modifications of the Daily Power System Operation Plan.................88
Execution of Works in Transmission Network ...........................................................88
Procedures Governing Execution of Works in Transmission Network..............89
Data Acquisition ....................................................................................................................90
V.3.4 Control in Disturbed State ...................................................................................................91
V.3.5 Technical and other Requirements for System Operation in Interconnection .....................92
V.3.6 Reports for Transmission System Operation........................................................................93
V.4 Power System Operation Plans in Emergency Conditions................................. 94
V.4.1 Introduction ...........................................................................................................94
V.4.2 Objectives ...........................................................................................................94
V.4.3 Operational conditions of EPS.............................................................................................95
V.4.4 Defence Measures Implementation ......................................................................................96
V.4.5 Plan for Protection System Operation .................................................................................97
V.4.6 Plan for Preventive Measures for Disturbance Elimination................................................98
V.4.7 Electricity Delivery Curtailment Plan..................................................................................99
Plan for Voltage Curtailment..........................................................................................100
Plan for Emergency Electricity Delivery Curtailment ............................................100
Immediate Emergency Electricity Delivery Curtailment......................................101
Long-term Electricity Delivery Curtailment ..............................................................102
V.4.8 Plan for Power System Restoration after Blackout............................................................103
Power System Restoration without External Source of Voltage (“black
start“)........................................................................................................104
Plan for Power System Restoration Plan with External Source of Voltage...105
V.5 Accidental outage ........................................................................................... 106
VI ACCESS TO THE TRANSMISSION SYSTEM ..................................................107
VI.1 Introduction .................................................................................................. 107

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VI.2 Objectives...................................................................................................... 107
VI.3 General provisions......................................................................................... 107
VI.4 The usage of transmission capacities within control area of TSO.................. 108
VI.5 The usage of the cross-border transmission capacities................................. 108
VI.6 Final operational plan.................................................................................... 109
VIINON-COMPLIANCE AND DISPUTE SETTLEMENT ........................................109
VII.1 Non-compliance of the User......................................................................... 109
VII.2 Non-compliance of TSO................................................................................ 110
VII.3 Material Liability of TSO and the Users ........................................................ 110
VII.4 Dispute Settlement ...................................................................................... 110
VIII INTERIM PROVISIONS .......................................................................111
Revision of the Code Provisions ............................................................................ 111
Harmonization with the Code Provisions .............................................................. 111
Harmonization of the general and other rules, agreements and contracts ........... 112
IX FINAL PROVISIONS.....................................................................................113
X APPENDIX 1 - TRANSMISSION SYSTEM PLANNING SCENARIO ................114
Definition .............................................................................................................. 114
Criteria .................................................................................................................. 114
Recommendation .................................................................................................. 115
XI APPENDIX 2 –METHODOLOGY FOR TRANSFER CAPACITY
ASSESSMENTS .............................................................................................117
Definition .............................................................................................................. 117
Methodology ......................................................................................................... 118
EVALUATION OF THE TOTAL Net Transfer Capacity Value .................................... 119
Evaluation of the Grid Transfer Capacity GTC ....................................................... 120
XIIAPPENDIX 3 –GUIDELINE FOR THE ASSESSMENT OF THE IMPACT OF
PROJECTS....................................................................................................121
Introduction.......................................................................................................... 121
Assessment criteria............................................................................................... 121
Evaluation Methodology........................................................................................ 123
Benefit Assessment............................................................................................... 125
XII.4.1 Geographical scope of the analysis.................................................................................125
XII.4.2 Benefit analysis 125
XII.4.3 Grid Transfer Capability Calculation .............................................................................126
Methodology for each benefit category................................................................. 127

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XII.5.1 Improved security of supply.............................................................................................127
XII.5.2 Social and Economic Welfare..........................................................................................128
XII.5.3 RES Integration 130
XII.5.4Variation in Losses (Energy Efficiency)...........................................................................131
XII.5.5 Variation in CO2 Emissions............................................................................................132
XII.5.6Technical resilience/system safety margin .......................................................................133
XII.5.7Robustness/flexibility........................................................................................................133
Assessment summary............................................................................................ 134
XIII APPENDIX 4 –TRANSMISSION SYSTEM ADEQUACY FORECAST ........135
Introduction.......................................................................................................... 135
XIII.1.1 Power balance 135
XIII.1.2 Definition for Adequacy .................................................................................................135
XIII.1.3 Reference points 135
XIII.1.4 Scenario for construction new power plants..................................................................136
Methodology ......................................................................................................... 136
XIII.2.1 Load 136
XIII.2.2 Load Management 137
XIII.2.3 Net Generating Capacity................................................................................................137
XIII.2.4 Unavailable Capacity.....................................................................................................138
XIII.2.5 Reliably Available Capacity...........................................................................................140
XIII.2.6 Remaining Capacity .......................................................................................................140
XIII.2.7 Exchanges 140
XIII.2.8 Margin Against Peak Load.............................................................................................141
XIII.2.9 Remaining Margin 141
XIII.2.10 Spare Capacity 142
XIII.2.11 Adequacy Reference Margin ........................................................................................142
XIII.2.12 Simultaneous Interconnection Transmission Capacity ................................................142
Analysis................................................................................................................. 146
XIII.3.1 Generation Adequacy.....................................................................................................146
XIII.3.2 Transmission Adequacy..................................................................................................147
XIV APPENDIX 5 – APPLICATION FORM FOR CONNECTION
APPROVAL ...................................................................................................150
XV APPENDIX 6 –OPERATIONAL NOTIFICATION PROCEDURE FOR
CONNECTION OF USER’S INFRASTRUCTURE TO TRANSMISSION
NETWORK....................................................................................................151
Operational Notification Procedure for Connection of New Power
Generating Modules to the Transmission Network...................................... 151
Compliance of Power Generating Modules to the Transmission Network............. 153
Compliance of the consumers objects or distribution systems to the
transmission network.................................................................................. 154

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XVI APPENDIX 7 –METHODOLOGY FOR ASSESSMENT OF
CONNECTION CHARGE ................................................................................157
Fee for construction of new connection, or upgrade of the existing one .............. 157
Participation fee for creation of technical conditions in the transmission
system......................................................................................................... 158
Transmission system infrastructure for construction of new connection.............. 159
XVII APPENDIX 8 – ADDITIONAL REQUIREMENTS FOR CONNECTION
OF GENERATION UNITS ..............................................................................160
General requirements ........................................................................................... 160
Synchronous generators connected directly to the grid........................................ 161
XVII.2.1 Active power 161
XVII.2.2 Frequency Stability .......................................................................................................161
XVII.2.3 Rеactive power control..................................................................................................164
XVII.2.4 Voltage Control System.................................................................................................165
XVII.2.5 Disconnection of the Production Facility from the Transmission System ....................167
XVII.2.6 Operation of production facility during disturbances...................................................168
XVII.2.7 System restoration169
Requirements for Power Park Modules................................................................. 170
XVII.3.1 Active power 170
XVII.3.2 Frequency Stability .......................................................................................................171
XVII.3.3 Voltage Stability and Reactive Power Control..............................................................171
XVII.3.4 Disconnection of the Production Facility from the Transmission System ....................172
XVII.3.5 Operation of production facility during disturbances...................................................173
Fault Ride Through Capability – Generator Type 2............................................................173
XVII.3.6 System restoration175
XVIII APPENDIX 9 – ADDITIONAL REQUIREMENTS FOR CONNECTING
THE DEMAND...............................................................................................175
XIX APPENDIX 10 – COMPLIANCE TESTING .............................................178
I.1. SYNCHRONOUS GENERATORS' UNITS.......................................................178
I.2. MODULES OF ENERGY PARKS ....................................................................182
I.3. CONSUMERS ...............................................................................................185
XX APPENDIX 11 – THE QUALITY OF ELECTRICAL ENERGY............................185
Flickers.................................................................................................................. 185
Harmonic distortion .............................................................................................. 186
Phase unbalance ................................................................................................... 187
XXI APPENDIX 12 – PROTECTION UNITS .................................................189

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XXII APPENDIX 13 –METODOLOGY FOR DETERMINATION OF
SECONDARY AND TERTIARY RESERVE .......................................................191
Determination of secondary control reserve......................................................... 191
Determination of tertiary control reserve ............................................................. 192

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Pursuant to the Article 69, of the Energy Law (“Official Gazette of MK”, no. 16/2011), and the
Article 19, point 18 of the Statutes of the Macedonian Electrical Transmission System J.S.C. for
transmission of electrical energy and control of electric power system, state owned company
MEPSO Skopje, upon the approval of the Energy Regulatory Commission, No. 02-2432/1 of
06.11.2014 has adopted:
THE GRID CODE – RULES FOR ELECTRICAL
TRANSMISSION SYSTEM OPERATION
I GENERAL PROVISIONS
I.1 Subject of the regulation
Article 1
(1) The Grid Code for transmission of electrical energy (hereinafter referred to as the „Code“)
regulates:
o Technical and other requirements for safe and reliable operation of the transmission system,
o Technical and technological conditions and methods of connection of users in accordance
with transparent and non-discriminatory principles,
o Conditions and methodology for determining fees for connection to the transmission system
in accordance with transparent and non-discriminatory principles,
o Terms and conditions for third party access to transmission system in accordance with
transparent and non-discriminatory principles,
o Objective, non-discriminatory and transparent procedures for resolving overloading in the
transmission system,
o Technical and technological requirements for production facilities in operation mode with a
temporary permit,
o Planning of the maintenance and development of the transmission system,
o Content of the transmission system development plan, as well as methods and procedures for
the submission of necessary data for development plan by the transmission system users,
o Methods and procedures for forecasting electricity consumption and the obligations of the
transmission system users (suppliers, production facilities and consumers directly connected
to the transmission system) to transmit the data necessary for making predictions,
o Measures necessary to maintain operational security of the transmission system,
o Measures, activities and procedures in case of disturbances and incidents,
o Functional requirements and accuracy class of measuring devices, and the method of
measurement of electrical energy and power,
o Criteria for the provision of system services,
o Dispatch of generation units in electric power system of the Republic of Macedonia,
o Quality of electrical energy (power quality),

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o Quality of services that TSO provides to the users,
o Communication protocols for system monitoring and control,
o Operation of the controlling system,
o Methods to publish information which the TSO is obliged to publish in accordance with the
Energy Law, and
o Methods and procedures for reporting to transmission system users.
I.2 Basic principles
Article 2
(1) The implementation of this Code is based on the following principles:
o Transparency, non-discriminatory and impartiality,
o Protect the public interest and rights of transmission system users,
o Reliability, security, continuity and quality of delivery of EE
o Efficiency and economy of operation of the TSO, and
o Minimum of prerequisites of the ENTSO-E related to the operation and exchange of EE
between synchronously connected systems.
I.3. Area of Implementation
Article 3
(1) TSO is the owner of the transmission network and is responsible for reliability, security and
quality of EE supply through the transmission network, ensuring the development and
maintenance of the transmission network for safe and efficient operation.
(2)The basic principles of delimitation of ownership and responsibilities between TSO and users of
transmission network are the boundary of delimitation. The boundary of delimitation is defined as
follows:
o If the user is connected to high voltage transmission network through system transformer
station, connected to at least two other transformer stations with two or more lines, power
transformer together with all high voltage equipment in transformer bay (disconnectors,
breaker, measurement transformers and surge arrestors) belongs to the user, while part of
high voltage equipment for connection of transformer bay to busbars belongs to TSO. Place
of delimitation is the terminal of busbar coupler toward high voltage busbars, and
o If the user is connected radially to the transmission network through high-voltage
transformer station and high voltage transmission lines, transformer station with radial lines
belongs to the user. Place of delimitation is the tension insulators on the portal system in
transformer station that belongs to the TSO.
(3)TSO has obligation to apply these Code in the management and use of:
o the transmission system, which includes power facilities, and other equipment for electrical
energy transmission at the 400 kV and 110 kV voltage levels, which are in TSO’s property
and

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o the parts of facilities and 110 kV network and higher which are either owned by transmission
system users or which they are entitled to exploit.
(4) In the EPS of the Republic of Macedonia, distinction of ownership or right to use the power
facilities and other equipment for the transmission of electrical energy as well as parts of the
facilities and network of 110 kV and higher voltage level, between TSO and transmission system
users is determined with the boundary of capital assets, as determined by individual contracts for
transmission network using, concluded between TSO and transmission system users.
(5) All electric power entities and transmission system users are obliged to apply this Code and to
comply in a manner of utilization of the transmission system in its operations.
(6) Electric power entities and users referred to in paragraph (5) of this article are:
o Electricity producers connected to the transmission system,
o Electricity distribution system operator(s),
o Electricity traders,
o Electricity suppliers,
o Users directly connected to the transmission system, and
o Other entities on the electricity market,
o Electricity market operator.
I.4 Basic Requirements and Responsibilities ensuing from the
Compliance with the Code
General Obligations
Committee for monitoring and implementation of the Code
Article 4
(1) TSO has the obligation to form Committee for implementation and realization of this Code
(hereinafter: Committee). Committee performs the following tasks:
o Supervision of Code implementation,
o Analysis of difficulties in Code implementation,
o Clarification of outstanding issues with regard to Code implementation,
o Drafting of proposals for Code modifications, and
o Prepare the opinion about necessity of making analysis of the benefits and costs,
o Prepare elaborated opinion for rejecting or approval of the Application for exception, and the
duration of the exception, at the request of TSO.
(2)The Committee consists of representatives from:
o TSO,
o electricity producers,
o energy entities performing the activity of electricity distribution,
o electricity traders,

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o electricity suppliers, and
o consumers directly connected to the transmission system.
(3) Representatives of the Energy Regulatory Commission may participate in the work of the
Committee without the right to vote.
(4) On the first session, Committee shall determine the list of members and adopt Rules for
Operation.
(5)The Chairman of the Committee is representative of the TSO.
(6) The Rules of Procedure of the Committee regulates:
o rights, obligations and responsibilities of the Committee members,
o the procedure of passing acts (interpretation, reports, recommendations, etc),
o meeting convening procedure,
o conditions to hold sessions,
o number of mandatory session annually, and
o procedures for issuing (publishing) of decisions, etc.
Amendments to the Code and its Interpretation
Article 5
(1) If any electrical energy entity considers that it is necessary to change the provisions of this
Code shall apply the procedure under Article 218 of this Code.
(2) Any electrical energy entity has the right to submit request to Committee in order to provide
additional interpretation related to aims and implementation of any part of the Code. Committee
has the obligation to provide requested interpretations and publicly to put at their disposal both
the request and the interpretation.
Unforeseen Events and Reporting
Article 6
(1) TSO is entitled to take contingency measures in case of the occurrence of events that are not
foreseen by the provisions of this Code, or the occurrence of which was impossible to prevent, and
the effect of such events may provoke the alteration of technical conditions for the exploitation of
transmission system and lead to consequences for the transmission system users.
(2) Any user has the obligation to comply with the instructions received from TSO.
(3) TSO informs the Committee and Energy Regulatory Commission of any unforeseen event and
of relevant decisions taken in accordance with this Code, within five (5) days
(4) TSO has the obligation to draft the report on the implementation of contingency measures for
unforeseen events, in the way and according to the procedure for the drafting of reports on
contingencies in the transmission system operation, defined in the Article 185 of this Code, which,
among other, will include the event that caused the unforeseen circumstance, measures taken and
effects and consequences of unforeseen event.

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(5) Committee has the obligation, within 45 days from the day of occurrence of unforeseen events,
to draft and submit to evaluation and agreement the initiative for amendment/supplement to this
Code, in accordance with unforeseen events.
Information and Data Confidentiality
Article 7
(1) Data submitted to TSO by energy entities and transmission system users are confidential and
TSO may disclose them to other energy entities or potential users only in cases and in the manner
described in this Code.
(2) The transmission system users determine the data related to technical characteristics and to
requirements for exploitation of their facilities, which are to be handled by TSO as confidential.
(3) TSO can publish information and data, indicated by the transmission system user as
confidential, only upon a written approval of the user. Such written approval determines for which
purpose the information or data may be disclosed.
(4) TSO is obliged to treat the data related to consumption, generation and exchange of electricity
of each individual user as confidential. Summary data of this kind, at the level of the electric power
system, are not deemed as confidential.
(5) Information for transmission system operation, including the information on disturbances and
other emergency situations, are not considered by TSO as confidential.
(6) Data on the transmission system load shall be disclosed by TSO in the form that does not
violate the confidentiality of information of the transmission system user.
(7) TSO exchanges corresponding data with the neighbouring transmission system operators,
which may include commercially confidential or sensitive data. In order to prevent eventual misuse
of such data, TSO concludes with neighbouring transmission system operators corresponding
contracts on confidentiality of available data, where such data are designated as confidential, and
the contractual parties undertake the obligation to comply with their confidentiality.
I.5. Terms, Abbreviations and Definitions
Terms
Article 8
(1) Definitions of certain terms contained in the Energy Law, are applied in the Code.
Definitions
Article 9
(1) Terms used in the Code have the following meaning:
AFLS-Automatic
frequency load
shedding
Shedding of the system load, achieved by disconnection of the
consumption of EE with the action of under-frequency relays

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Active Energy Energy that can be converted into other energy, e.g. mechanical,
thermal, chemical, sound or light energy.
Active power Electrical power available for conversion into other power e.g.
mechanical, thermal, chemical, sound or light. It is the average product
of the instantaneous values of voltage and current in a given time
interval.
Database of
measurement
Database that contains the verified measurement data.
Balancing Group Balancing group consists of one or more participants from the electricity
market of which one member of the balancing group takes full balance
responsibility party.
Balance
Responsibility
Responsibility of balance responsible entity to provide a balance
between whole declared production, procurement and import of
electricity from one side and declared consumption, sales and export of
electricity, on the other hand, for one or more connection points and/or
for one or more bilateral transactions.
Balance
Responsible Entity
Electricity market players which undertake balance responsibility and
deliver physical schedule (nominations) for the balance group in
accordance with their mutual contractual obligations
Block Coordinator TSO from control block, responsible for secondary regulation of control
block, for the calculations of the control area of the control block, for
organization on the secondary regulation inside of the block and for
coordination of the programs for exchange between control areas in the
block and the programs of the exchange with neighbouring control
blocks
High Voltage Nominal voltage 110 kV and higher
Force majeure All unpredictable natural phenomena, events and circumstances which
are determined by law.
Generator unit Device which consists of all the equipment necessary for production of
electricity
Imbalance of EPS Deviation from the exchange program, i.e. the difference between the
available energy (generation and import) and total demand
(consumption, export and system losses)
Dispatch Centre
TSO
Centre for electric power system (or control area) management
Dispatch Control of power flows in the electric power system, including the
electricity production and electricity exchange with other systems

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Bilateral operating
contract
Contract between TSO of Republic of Macedonia and TSOs of
neighbouring systems on the joint parallel operation carried out through
common, interconnection lines – interconnectors
Power Plant Electric power facility that includes one or more generation units
Energy Balance Quantity of EE which is engaged with the activation of system services
for alignment of the deviations between the available EE and
consumption of EE in real-time.
Frequency Set-point Frequency established by TSO in accordance with ENTSO-E
recommendations, as the desired operational system frequency
Exemption Approval, issued by the Energy regulatory commission or by TSO at the
request of the transmission system user, for non-compliance with any
of the provisions of the Code for a limited period of time, i.e. until the
reasons for which the exemption has been requested cease to exist
Dispatch
Instruction
Instructions issued by the EPS operational manager, related to the
operation of generation units, transmission and user systems, including
the use of ancillary and system services
Control Block Control block consists of one or several control areas that operate
jointly in order to ensure the load-frequency control with respect to
other control blocks of synchronous area.
Control Area The smallest part of EPS that has its own control system for
production/consumption of EE and frequency, usually coincides with the
territory of states and managed by the one TSO
Metering Point Point of physical connection in the EE measuring system for electrical
energy register and electrical parameters measurement
Metering equipment It consists of measurement transformers, secondary measuring circuits,
meter, protection, communication and supervisory equipment.
Metering Data Data obtained from parameters of EE, contained in the electric meter
registry.
Metering System A set of metering points.
Connection Point Point in the EPS where the generator units, customers and distribution
systems are connected to the transmission network where TSO delivers
/ EE receive to / from the user of transmission system.
Power park module Any generator unit or ensemble of units generating electricity which is
not synchronously connected to the network. This includes any
connection through power electronics and any ensemble of units having
a single Connection Point to the network

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Network
parameters
Network parameters are indicators which quantify physical properties of
the network elements: the line axial impedance, the line admittance,
impedance between two nodes of the network, the transformation ratio
(turns ratio) of the transformer, etc.
Load shedding Reduce of EE consumption in a controlled manner with switching off the
consumers in the event of disrupted / disturbed integrity of EPS, to
bring it back in normal or transient state.
Voltage
Transformer (VT)
Transformer used with metering systems and/or protection devices with
function of transmitting the primary voltage variable to the secondary
values as accurately as possible according to its magnitude and angle.
Voltage Flicker Sudden change of voltage wave usually caused by the connection of
user’s plant which distorts the normal sinus voltage curve
Disturbed operating
mode
Operating mode which deviates from normal operation.
EPS normal
operation
EPS normal operation which considers operation points of system
parameters with sufficient security margin.
Load Load is a power supplied to the system or part of the system or
consumers and is expressed in kW or kVA, or MW or MVA.
EPS operating
leader
Expert with authorization to leads EPS of Macedonia
Island The part of the EPS physically separated from the main interconnection
system which forms an islanded EPS. The operation of facilities in that
system is called the island operation.
Capability diagram
of Generator Unit
Document which determines limits of capability of operation of
generation unit (in MW and MVAr) under normal operating conditions
Underfrequency
Relay
Electric metering relay triggered by a system frequency drop below
defined relay set-points
Auxiliary Equipment Any part of the equipment and/or plant that is not directly the part of
the EPS, but is necessary for its operation
Exchange Program Exchange program represents the total planned exchange between
control areas or between two control blocks.
Operating variables Operating variables are quantities that characterize a certain operation
of EPS
Accounting
measurement
Measurement of electrical energy whose data are used for preparing
TSO financial documents (invoices).

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Primary Control Primary control is automatic decentralized function of turbine controllers
of generation units that makes balance between production of
generator units and consumptions of EE in the synchronous area.
Automatic function of turbine controllers enables the changes in
production of the generation unit due to frequency changes
Primary Reserve A positive or negative part of the total active power bandwidth for
primary regulation, measured from setpoint of generator unit before
disturbance occurs to the maximum power for primary control.
System Blackout Situation in which all generation is stopped and there is no supply of
electricity from other systems, which makes the whole system switched
off, i.e. total no-voltage condition in the control area.
Reactive Energy Electric energy not consumed but existing between the system units
with established electric fields and system parts with the established
magnetic fields, however its flow increases current and system losses.
Reactive Power Electric power required for establishment of electric and magnetic fields.
In a chiefly electric field, reactive power is capacitive, while in chiefly
magnetic field –reactive power is inductive.
Voltage and
Reactive Power
Control
Management of generation of reactive power in transmission system
with generators, synchronous compensators, static compensation
systems and reactive power flows management with changing
transformation ratio by switching on/off transmission system elements
Load-frequency
Control
Automatic centralized function that regulates the production in the
control area using the secondary regulation reserve, in order to:
-maintain the exchange program with all other control areas at the
given value, and
-maintain the frequency to its default value in order to relieve the
reserve used for primary control.
Secondary Reserve A positive or negative part of the total active power bandwidth for
secondary regulation, measured from setpoint of generator unit to the
maximum/minimum power for secondary control.
Synchronous Zone Synchronous Zone is area of interconnected control areas.
System Losses Active energy losses in transmission system elements
System Stability Capability of EPS to maintain the stability during normal or disturbed
operational regimes as well as to achieve an acceptable new steady
state after the occurrence of a disturbance.
Black Start
Capability of
Generators
Capability of a generating unit to start-up, without an external voltage

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Current
Transformer (CT)
Transformer used with metering and/or protection devices in which the
current is in secondary winding, within the limits of predefined error,
proportional and in phase with the current in primary winding.
Tertiary Control Automatically or manually change of operating points of the generation
units aimed to restore the secondary reserve
Tertiary Reserve Component of EPS reserves available within 15 minutes, activated with
the aim to restore the secondary reserve.
Flicker It is occurrence of a disturbances in human sight when the illumination
of a lighting fixture changes during the time ((i.e. the impression of
flickering light), as a result of the occurrence of voltage fluctuations
caused by the plants belonging to users of the transmission or
distribution system..

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Abbreviations
Article 10
The Abbreviations used in the Code shall have the following meaning:
AMR/MDM System for automated collection, storage and processing of data from the EE
metering equipment
ARS Automatic Reclosure System
AAC Already Allocated Capacity
ACE Area Control Error
AGC Automatic Generation Control
ATC Available Transmission Capacity
BRP Balance Responsible Party
EPS Electric Power System
EE Electrical energy
EC European commission
EU European union
ENTSO-E European Network of Transmission System Operators for Electricity
ENTSO-E CE European Network of Transmission System Operators for Electricity –
Continental Europe
FACTS Flexible Alternating Current Transmission System
Y Current year
GTC Grid Transfer Capacity
IEC International Electrotechnical Commission
ISO International Standards Organization
ITC Inter TSO Compensation
M Current month
VT Voltage Transformer
NTC Net Transfer Capacity
DSO Distribution System Operator
TSO Transmission System Operator

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RES Renewable Energy Sources
MO Market operator
ERC Energy regulatory commission of the Republic of Macedonia
RgIP Regional Investment Plan for South East Europe
SCADA/ЕМS Supervisory Control Аnd Data Acquisition / Energy Management System
SAF System Adequacy Forecast
SOAF Scenario Outlook and Adequacy Forecast
CT Current transformer
ТHD Total Harmonic Distortion
TTC Total Transfer Capacity
TYNDP Ten-Year Network Development Plan
VT Voltage transformer
VUF Voltage Unbalance Factor

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II TRANSMISSION SYSTEM DEVELOPMENT PLANNING
II.1 Scope and Objectives
Planning-related Activities
Article 11
(1) The main objective of transmission system planning is to ensure, with respect to mid and long
term horizons, the development of an adequate transmission system which:
o Ensures safe system operation,
o Provides a high level of security of supply,
o Contributes to a sustainable development,
o Access and connection to the transmission network for all market participants,
o Development of the EE market, and
o Efficiency.
(2) In this process have to be kept in mind, in particular:
o National legislation and regulatory framework;
o EU policies and targets;
o Requirements and general regulations of the liberalised European power and electricity
market set by relevant EU legislation;
o Security of people and infrastructure;
o Environmental policies and constraints;
o Transparency in procedures applied;
o Economic efficiency.
(3) Transmission system development includes:
o Construction of new transmission system elements,
o Reinforcement of existing transmission system elements (reconstructions and capacity
upgrade),
o Adjustment of protection systems and their modernization,
o Reconfiguring of network topology, and
o Permanent monitoring and implementation of new technological solutions.
(4) National development plans must be in coordination with ENTSO-E Regional Investment Plans
(RgIP), System outlook and Adequacy forecast (SOAF) the Community-wide Ten Year Network
Development Plan (TYNDP), as ratified by EC Regulation 714/2009.
Planning-related Rights and Obligations of TSO
Article 12
(1) TSO plans the transmission network development in a way that will ensure its safe and
economically justifiable operation in the interest of all users under this Code.

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(2) In order to ensure the long-term and medium-term planning of transmission system
development, TSO is responsible and obligated for:
o TSO creates transmission development study for 10 year planning period, updates this study
as needed, at least once in three years period, and published on its website,
o For each year TSO is obliged to adopt a transmission development plan for the period of next
five years. TSO submits the plan to the Energy regulatory commission by October 31st
and,
after obtaining approval from the Energy regulatory commission, plan shall be published on
its website, and
o For each regulated period TSO prepares transmission system investment plan, which in
particular shows the expected increase in work efficiency of the transmission system by
reducing electricity losses and improving the quality of delivered electricity as a result of the
planned investments. This plan shall be submitted to the Energy regulatory commission for
approval.
Planning Concept
Article 13
(1) Planning Concept consists of:
o definition of input data,
o definition of models and scenarios,
o definition of technical criteria,
o scenario analysis,
o proposal of solutions,
o evaluation of solution proposals ,
o plan acceptance, and
o plan implementation.
II.2. Input and Basic Data
General requirements
Article 14
(1) In the process of transmission system development planning, TSO takes in consideration the
following input data and information:
o Data trends for production/consumption of the transmission system users,
o Development of existing, and projects for new electricity facilities, planned by the users in
Republic of Macedonia and operators of neighbouring transmission systems, as defined in
their development plans,
o Forecasts of EE balance and power,
o Surveys for the justification of investment in transmission system planning,

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o Any possible disturbance conditions in the system that may occur during the operation as
well as needs ensuing from such situations,
o Issued Connection approvals of new users to the transmission system, and
o Other environmental and safety regulations.
EE and Power Demand Forecast for users
Article 15
(1) Basic input data necessary for the EE and power demand forecast are:
o Values of EE demand (MWh) and active power (MW), with special attention paid to values in
characteristic regimes of winter and summer peak and off-peak,
o Connection requests of direct consumers to the transmission system,
o Dynamics of economic development of the country (on the basis of the forecast of gross
national product growth, investments, employment and consumption), and
o Change of EE consumption in different economic sectors, in order to establish the link
between the economy and the EE demand.
(2) At request of the TSO, each user is obligated to submit their forecast for EE and peak power
demand for short, medium and long-term planning period.
Data from EE producers
Article 16
(1) Input data for EE producers, are:
1) Data on existing power plants
o technical constraints in production (minimum and maximum active and reactive power) and
possible changes due to planned overhaul
o upgrading/downgrading of generation capacities or decommissioning of generation units;
2) Data on new power plants
o If the planned year of commissioning of the plant falls on the planning period from 3-5
years and the facility is in the phase of submission of request for connection, it is necessary
to submit to TSO detailed data according to the request for connection of user, pursuant to
the Article 67 of this Code.
o For the planning period beyond 5 years, and if detailed data are unavailable, the following
basic data are necessary:
 Minimum and maximum of active and reactive power of the future power plant,
 Primary energy source,
 Power plant location, and
 Dynamics of construction.
(2) Data on energy sources from neighbouring systems connected to the transmission system are
collected at the level of basic data and, depending on the influence, are taken in consideration in
appropriate way in definition of basic operations scenarios of the planned operation of
transmission system of Republic of Macedonia.

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Forecast of EE and Power Balance
Article 17
(1) Forecast of electricity and power balance for the EPS of the Republic of Macedonia represents
summary of collected forecast data from all transmission network users for mid-term and long-
term period.
(2) On the basis of this data, TSO carries out the analysis of potential surpluses/deficiencies of EE
and power in EPS of Republic of Macedonia and evaluates total EE exchanges with neighbouring
systems.
(3) On the basis of such analysis and evaluation of the situation on the regional EE market,
probable exchanges on interconnection lines are established.
Harmonization of Development Plans with Transmission System Users
Article 18
(1) Transmission system development plan is primarily based on development plans of existing
and potential transmission system users and in that respect must be harmonized with their
development plans.
(2) In order to ensure that development plans between TSO and other responsible entities are
mutually harmonized on a satisfactory level, the coordination of corresponding activities related to
system development is carried out already at the planning phase.
(3)TSO and other responsible entities must achieve a fast and timely communication related to all
system modifications that may have influence on each other.
(4) For the purpose of coordination of future activities and harmonization of development plans,
TSO regularly publishes updated available data relevant for the transmission system development.
Parties interested in getting connected to the transmission system may submit to TSO their
proposals and comments to published data, by the date indicated as the deadline for public
collection of data.
(5) TSO, upon the expiry of deadline from the paragraph above, submits the following collected
data to concerned entities, for verification and update if necessary:
1) To electricity producers:
o Available data on planned replacement of equipment, upgrading/downgrading of
generation capacities or decommissioning of existing generation capacities and
o Available data on new generation units (installed capacity, primary energy source,
geographic location, dynamics of construction);
2) To the distribution system operator:
o Forecast of demand increase in characteristic regimes relevant for the planning per
distribution area,
o Geographic distribution of forecasted demand on existing and planned substations in
accordance with statistical data from the past and available information on displacement
of centres of consumption,
o Data on planned changes of capacities in existing transformer stations,
o Data on planned construction and connection of new substations, dynamics of their
construction and location in accordance with available data on geographic distribution of
load and in accordance with spatial planning documentation that is in force, and

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o Available information on installation (replacement) of equipment in facilities of users
that may be relevant for the quality, security and reliability of operation of the entire
transmission system;
3) To direct consumers of transmission system:
o Current data on planned upgrading/downgrading of peak demand or decommissioning
of parts of facilities for existing users and
o Current data on new facilities (peak demand, geographic location of facility, dynamics of
construction);
4) To operators of neighbouring transmission systems:
o Data on development plans, relevant to neighbouring transmission systems, are
harmonized by TSO at the level of regional working groups;
5) To state and local self-government bodies competent for the preparation of spatial planning
documentation:
o Data on planned construction and connection of new transformer stations, dynamics of
their construction and location in accordance with available data on geographic
distribution of load.
(6) If responsible entities fail to submit objections on, or modifications of data within 3 months
from the day of the submission of data, it is considered that published/submitted data are verified.
(7) After the expiry of the deadline from the paragraph above, once a year, TSO submits to the
competent Ministry and the Energy regulatory commission for verification the draft basic data for
the preparation of planning document that contains publicly collected data on electricity generation
and demand, verified and updated by producers, DSOs, eligible consumers, neighbouring system
operators and bodies responsible for the preparation of spatial planning documentation.
(8) By publishing the transmission system development plan on the official web site, TSO makes
all necessary information, relevant for the development of transmission system of Republic of
Macedonia, transparent to users and operators of neighbouring systems.
II.3. Models and Scenarios
Market model
Article 19
(1)TSO prepares a market model which contains technical, economic and financial parameters of
the generation and demand by region, covering different time horizons.
Network model
Article 20
(1)TSO prepares network model that reflects the configuration of EPS i.e. gives a picture of
connections and operation principles of power system elements.
(2) Depending on the type of analyses, models with different level of details of the network are
used. It is based on a power system database at a given time horizon, containing the following
elements:
o Electrical parameters of the network; topology
o Power plants information per node; types of generators

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o Information per node: generation and consumptions
o Covering different time horizons and grid development scenarios.
National model
Article 21
(1) TSO prepares national model for EPS of Republic of Macedonia that contains all network
elements for 110 kV and 400 kV voltage level. Generators are modelled on the generator voltage
level, together with step-up transformers. In thermoelectric power plants auxiliary service
consumption is modelled. Load of distribution substations are modelled at 110 kV, while for the
purpose of single-phase short circuit current calculation 110/X/Y kV distribution transformers are
modelled with respect to the winding connection type. For dynamic stability analyses, models of
the power system elements are supplemented with dynamic features.
Regional model
Article 22
(1) The regional model consists from national transmission network of the south-eastern Europe
countries and takes into account all regional projects (defined in regional group for system
planning in ENTSO-E Continental Southeast Europe) and the equivalent of the rest of ENTSO-E
interconnection. Electric power system of Republic of Macedonia is integrated into the regional
model.
Planning scenarios
Article 23
(1) TSO uses the planning scenarios to define different concepts for network development, which
are dictated by uncertainties in the forecast procedure by considering a demand forecast, a
generation patterns and a set of exchange patterns for systems outside of the region within the
scope of Study for development of the transmission network.
(2) TSO prepares scenarios for planning, based on:
o demand growth (uncertainty in the forecast of distribution and direct consumers
demands),
o location and installed power of the new power plants,
o variation of hydrological conditions, which reflects the variation of power for import or
export,
o regional transit capacity in different directions, and
o integration of renewable energy sources.
(3) Criteria and recommendations for defining transmission system planning scenarios are given in
APPENDIX 1 - TRANSMISSION SYSTEM PLANNING SCENARIO.
II.4 Technical analyses and criteria for planning
II.4.1 Technical analyses
Analysis of normal operating regime

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Article 24
(1) TSO uses the normal operating regime as the basis for transmission system technical analysis.
Contingency Analyses
Article 25
(1) TSO makes an analysis for loss of one or several elements of the EPS, defining the following
contingency:
o A normal contingency is the loss of one of the following elements:
- Generator,
- Transmission circuit (overhead, underground or mixed),
- A single transformer or two transformers connected to the same node,
- Shunt device,
- Single DC circuit,
- Network equipment for load flow control (phase shifter, FACTS), and
- A line with two or more circuits on the same towers if TSO considers this as
relevant and includes this contingency in its normal system planning.
o A extreme contingency is the loss of one of the following elements:
- A line with two or more circuits on the same towers if a TSO considers this as not
relevant and does not include this contingency in its normal system planning,
- A single busbar,
- A common mode failure with the loss of more than one generating unit or plant,
and
- A common mode failure with the loss of more than one DC link.
o A most extreme contingency is the loss of one of the following elements:
- Two lines independently and simultaneously,
- A total substation with more than one busbar, and
- Loss of more than one generation unit independently.
N-1 Security Rule
Article 26
(1) The N-1 security rule is satisfied if the network parameters are within acceptable limits for
expected transmission and supply situations as defined in chapter II.4.2 Technical criteria for
network parameters assessment, for network parameters assessment from this Code, for expected
network conditions defined by the planning scenarios, for a temporary (or permanent) outage of
one of the elements of the normal contingency list.
Market Analyses
Article 27

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(1) TSO with market based analyses gives a detailed assessment of generation and consumption
profile, using a simplified representation of the grid. Market analyses performing hourly analysis
throughout the year have the advantage of clearly highlighting the structural rather than incidental
“bottlenecks” in the network.
Network Analyses
Article 28
(1) Network assessment is carried out by TSO on a sample of planning scenarios, selected on the
basis of information given by the market analyses. It has a simplified representation of generation
and demand profiles, and a detailed representation of the grid.
Load Flow Analyses
Article 29
(1) The calculation of power flows and voltage profiles in stationary conditions for normal
operating regimes (with all network equipment available) of the transmission system determines
the following:
o loadings on lines and transformers,
o network voltage profile,
o production of active and reactive power of power plants, and
o losses of active power in the transmission system.
(2) Examination with N-1 rule is carried out by TSO taking into account normal contingency of all
elements in transmission system.
(3) Examination of rare contingencies only for specific cases is carried out by TSO. This kind of
assessment is based on the probability of occurrence and/or based on the severity of the
consequences in order to prevent interruptions in the wider area.
(4) In the process of planning TSO not include most extreme contingency. Most extreme
contingency are analysed through Defence Plans.
(5) In cases of failures combined with maintenance, TSO analysed non-availabilities of one
element combined with a failure of another. Such investigations are done by the TSO based on the
probability of occurrence and/or based on the severity of the consequences, and are of particular
relevance for network equipment that may be unavailable for a considerable period of time due to
a failure, maintenance, overhaul during major constructions.
Grid Transfer Capability Analyses
Article 30
(1) TSO carries out the Grid Transfer Capability (GTC) analyses in order to determine the ability of
the grid to transport EE across a boundary from one area (price zone, area within a country or a
TSO) to another. The methodology for calculating the Grid Transfer Capability is provided in
APPENDIX 2 –METHODOLOGY FOR TRANSFER CAPACITY ASSESSMENTS, and APPENDIX 3 –
GUIDELINE FOR THE ASSESSMENT OF THE IMPACT OF PROJECTS.
Optimal Power Flow Analyses
Article 31

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(1) TSO performs optimal power flow analyses which are used to determine optimal values of the
control variables in the EPS.
Short-circuit Analyses
Article 32
(1) TSO performs analysis for maximum and minimum symmetrical and single-phase short-circuit
currents are evaluated according to the МКС EN 60909, in every bus of the transmission network.
Voltage Stability Analyses
Article 33
(1) TSO performs analysis of voltage stability refers to the ability of a power system to maintain
acceptable voltages at all buses in the system under normal conditions and after a disturbance.
Dynamic Stability Analyses
Article 34
(1) TSO performs dynamic stability analysis taking into account rotor angle stability, i.e. ability of
synchronous generators of an interconnected EPS to remain in synchronism after a disturbance.
Rotor angle stability problems can be divided in two categories:
o small-signal stability, and
o transient stability.
(2) TSO performs dynamic stability analyses in all cases where problems with stability can be
expected, based on TSO operational experience.
Reliability Analyses
Article 35
(1) TSO performs reliability analyses to identify network bottlenecks not only according to the N-1
rule, but ones caused by multiple outages with relatively high probability.
(2) Indicator of the reliability of a transmission network element is its availability and unavailability,
respectively. Unavailability is defined as a time interval within the observed period of time (usually
one year) when a network element is out of operation.
(3) The transmission system indices which are indicating the level of EE reliability supply are:
o EE Not Supplied (EENS), and
o Loss Of Load Probability (LOLP).
(4) Probabilistic algorithms are used for the calculation of the parameters in the previous
paragraph, which use occurrence and duration of the transmission system elements outages as
input data.

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II.4.2 Technical criteria for network parameters assessment
Steady state criteria
Article 36
(1) In transmission system planning, TSO uses the following criteria to determine the steady state:
o Cascade tripping - A single contingency must not result in any cascade tripping that may
lead to a serious interruption of supply within a wide-spread area.
o Maximum permissible thermal load -The normal operating regime and regime with
contingency must not result in an excess of the permitted rating of the network equipment.
Taking into account duration, short term overload capability can be allowed, but only
assuming that the overloads can be eliminated by operational countermeasures within the
defined time interval without endangering the overall system security.
o Maximum and minimum voltage levels - The normal operating regime and regime with
contingency shall not result in an excess of the admissible voltage boundaries, defined for
planning purposes:
o 380 - 420 kV for 400 kV voltage level, i.e. ±5% of nominal voltage,
o 99 - 121 kV for 110 kV voltage level, i.e. ±10% of nominal voltage.
Maximum loss of load/generation criteria
Article 37
(1) In the transmission system planning, TSO uses the following criteria for maximum loss of load
or generation:
o loss of consumption or production should not exceed the power of the largest consumer and
the largest generator unit in the system.
Short circuit criteria
Article 38
(1) In the transmission system planning, TSO uses the following criteria for short-circuit current:
o The rating of equipment shall be able to withstand the initial three-phase and single-phase
short-circuit current (e.g. the make rating) when energising on to a fault and the short circuit
current at the point of arc extinction (breaker rating). Minimum short-circuit currents must
ensure reliable operation of protection equipment.
Voltage stability criteria
Article 39
(1) In the transmission system planning from the aspect of voltage stability, TSO uses the
experience and recommendation of ENTSO-E.
Dynamic stability criteria
Article 40

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(1) In the transmission system planning, TSO use the following criteria for dynamic stability:
o Transient stability -Any 3-phase short circuit, successfully cleared by the primary protection
system in service, shall not result in the loss of the rotor angle stability and the disconnection
of the generation unit unless the protection scheme requires the disconnection of a
generation unit from the grid, and
o Static stability - Possible phase swinging and power oscillations, triggered by switching
operation or bulk power transits, in the transmission grid shall not result in poorly damped or
even undamped power oscillations.
II.5. Solution proposals
Identification of the problems
Article 41
(1) TSO is obliged to start with planning of reinforcement of the transmission system, if the
assessment criteria for network parameters given in Articles 36 - 40 of this Code, are not met.
(2) If technical criteria are not satisfied when analysing the scenarios, problems should be noticed
and possible solutions should be identified by TSO.
Time frame for solution implementation
Article 42
(1) Time framework for solutions implementation include: short-term (Y+1, Y+2 and Y+3), mid-
term (Y+5) and long-term planning horizon (Y+10).
(2) For analysed conditions in years Y+1, Y+2 and Y+3, that belong to the short-term planning
horizon, all outages in which transmission system does not meet the technical criteria from Articles
36 – 40 of this Code, shall be identified as critical. TSO dismiss the identified problems with
possible corrective actions, since the implementation of solutions for upgrade and or reconfigure
topology in the transmission system, takes long time (depending on the type of solution, from
three to eight years).
(3) In mid-term (Y+5) and long-term (Y+10) planning horizon, for all outages in which
transmission system does not meet the technical criteria from Articles 36 – 40 of this Code, and
where corrective dispatching actions cannot be implemented. Reinforcement solution for
transmission system by investments in new elements shall be proposed.
Guidelines for transmission system development
Article 40
(1) TSO uses the following general guidelines for transmission system development:
o For supplying the areas in which 400 kV voltage level is not envisaged, 110 kV double circuit
OHLs with a classic type of conductor ACSR 240/40 mm2
should be used,
o For construction of new 400/110 kV substation, transformer with 300 MVA rated power
should be used,
o For construction of new 110 kV single circuit OHL in transmission system of Republic of
Macedonia, classic type of conductor ACSR 240/40 mm2
should be used,

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o For construction of new 110 kV transmission lines in Skopje region, classic type of conductor
ACSR 360/60 mm2
should be used for overhead lines, and
o New cables in 110 kV transmission lines should be type XLPE Al 1000 mm2
.
Possible solutions
Article 44
(1) Measures for solving the problems include, but not limited to, the following:
o Resetting of control and protection devices of all elements in EPS,
o Reinforcement of overhead circuits to increase their capacity (e.g. increased distance to
ground, replacing of circuits, hot conductors),
o Doubling of cables to increase rating,
o Replacing of network equipment or reinforcement of substations (e.g. based on short-circuit
rating),
o Extension of substations and construction of new ones,
o Installation of reactive-power compensation equipment (e.g. capacitor banks),
o Addition of network equipment to control the active power flow (e.g. phase shifter, series
compensation devices),
o Additional transformer capacities, and
o Construction of new circuits (overhead and cable).
II.6. Project Assessment
General
Article 41
(1) TSO is obliged to make project assessment, for determination the impact of transmission
projects, both in terms of added social welfare (increase of capacity for trading of energy and
balancing services between price zones, RES integration, increased security of supply) as well as in
the terms of costs.
(2) The evaluation of the effects may be performed using both market studies and network
analysis, including expert assessment, is provided in APPENDIX 3 –GUIDELINE FOR THE
ASSESSMENT OF THE IMPACT OF PROJECTS.
Project
Article 42
(1) Project comprises one or several investments that have to be realised in total to achieve a
desired effect.
(2) Internal project serve for reinforcement of internal (national) grid.
(3) An interconnection project may be composed by the cross-border line, as well as internal
reinforcements necessary to achieve the desired increase in cross-border transmission capacity.
(4) If influence of the given internal project on increase of transmission capacity is more than 20%
it has regional importance and could be considered as a part of interconnection project.

GRID CODE
25
Interconnection Project
Article 43
(1) Main drivers for new interconnection lines are:
o integration of EE market,
o jeopardized security and stability in EPS,
o violated reliability of EE supply, and
o congestion on the cross- border capacities for a long time period.
(2) Analyses of the necessity for new interconnection line include:
o Regional market and network simulations and definition of potential candidates, and
o Bilateral and regional feasibility interconnection studies.
(3) Needs for development of interconnection links are identified by TSO together with foreign
partners responsible for transmission system development. TSO cooperates with transmission
system operators at the regional level and at the level of ENTSO-E in studying interconnection
projects.
Benefit Categories
Article 48
(1) TSO applies the following benefit categories according to ENTSO-E recommendations:
o [B1] Improved security of supply is the ability of an EPS to provide an adequate and secure
supply of electricity in normal conditions.
o [B2] Social and economic welfare is characterised by the ability of a power system to reduce
congestions and thus providing an adequate grid transfer capability. The reduction of
congestion as an indicator of social and economic well-being implied equal distribution of
benefits as one of the objectives of the European Union to develop an integrated market.
o [B3] RES integration. Support to RES integration is defined as the ability of the EPS to allow
the connection of new RES plants or to allow reduction of undelivered energy of existing
RES.
o [B4] Decreasing of losses in the transmission grid is the characterisation of the evolution of
thermal losses in the transmission network. In the same time, it is an indicator of energy
efficiency.
o [B5] Decreasing of CO2 emissions is the characterisation of the evolution of CO2 emissions
as a result of RES integration and decreasing of EE losses in the transmission network
(combination of [B3] and [B4]).
o [B6] Technical resilience/system safety is the ability of the EPS to withstand extreme system
conditions, and
o [B7] Flexibility is the ability of the proposed reinforcement to be adequate in different
possible future development paths or scenarios, including trading of balancing services.
Project costs
Article 49

GRID CODE
26
(1) Total project expenditures are based on prices used within each TSO and rough estimates on
project main characteristic. Land costs, costs of obtaining permissions and life cycle depreciation
costs should be also considered in estimation.
Social and Enviromental Impact
Article 50
(1) TSO is obliged to make project assessment for social and environmental impacts.
Spatial Planning Criteria
Article 51
(1) On the base of analysis of spatial planning documentation, TSO evaluate the possibilities for
the construction of new transmission system elements, define new corridors for the construction of
overhead lines (or cable installation) and possible most suitable locations for the construction of
new transformer stations and to establish necessary modifications and updates of existing spatial
planning documentation, of which the competent entities have to be informed.
Environmental and Technical Needs for System Rationalization
Article 52
(1) TSO evaluates development activities also from the aspect of system rationalization, in order to
improve the quality of service provision and at the same time comply with environmental
protection requirements, taking also in consideration geographic and environmental specific
features of the area anticipated for the path of overhead lines or location of electricity facility.
(2) Projects that include the dismantling of parts of lines or facilities that have reached the end of
their operational age and that are no longer considered necessary for the security of system
operation, or projects which constrict possibilities for construction of new transmission system
elements must be included in activities related to TSO transmission system planning.
Sensitivity Analysis
Article 53
(1) As a part of project evaluation, TSO has the right to make sensitivity analysis which is used to
determine how “sensitive” is a project on changes in the value of the input assumptions (economic
parameters or scenarios).
II.7. Transmission Development Study
General
Article 44
(1) TSO is obliged to prepare transmission network development study (Study) that contains
strategy for development of the transmission system of Republic of Macedonia. Study includes the
activities over a ten-year planning period as well as basic guidelines for the development after the
ten-year period, which gives the possibility to existing and potential users to evaluate the
feasibility of connection to and exploitation of the EPS.

GRID CODE
27
(2) The Study comprises necessary measures for ensuring secure and reliable supply of all
consumers and maintaining operational characteristics of the transmission network in accordance
with analysis and planning criteria from Articles 36 – 40 of this Code, with the lowest transmission
network development costs.
Methodology
Article 55
(1) Methodology for Study preparation consists of the following steps:
o Collection, analysis and definition of input data,
o Definition of scenarios,
o Modelling of the transmission network,
o Plan for rehabilitation of existing lines,
o Analysis of the base case and N-1 security rule for the reference year for all defined
scenarios (power flows and voltage profiles, and determination of optimal reactive power
production, if necessary),
o Identification of possible limitations in the transmission system based on defined technical
criteria for assessment of operational variables given in Articles 36 – 40 of this Code,
o Creating the list of possible projects for network reinforcement,
o Project assessment for network reinforcement (APPENDIX 3 –GUIDELINE FOR THE
ASSESSMENT OF THE IMPACT OF PROJECTS),
o Defining the final network configuration for the reference year,
o Transmission capacities calculation,
o Short-circuit current calculation and control/verification of technical specification for
equipment.
o Dynamic stability calculation and determination of the measures for its preservation.
o Creation of Strategic Plan for transmission system.
Integration of Study in Pan-European and Regional Plans
Article 56
(1) Models, forecasts and main conclusions of the Study TSO submitted to the relevant institutions
to should be integrated as part of regional investment plan of SEE (RgIP-Regional Investment plan
for South East Europe), ten-year plan for development of transmission network (TYNDP - Ten Year
Network Development Plan) and forecasts of the system adequacy (System Adequacy Forecast)
inside of ENTSO-E.
II.8. Preparation of Plan
Strategic plan for transmission system
Article 57

GRID CODE
28
(1) Transmission development study determines the solutions which should be implemented in the
transmission system of Republic of Macedonia in order to provide secure and reliable operation of
EPS. These solutions are displayed in the form of a Strategic Plan for EPS.
(2) The EPS Strategic plan contains a list of:
o Corrective measures,
o New connections of the transmission system users,
o Facilities envisaged for the reconstruction and revitalization,
o New objects for transmission system strengthening, and
o New interconnection lines with neighbouring EPS’s.
(3) Solutions are grouped in terms of time horizon according to the Article 42 of this Code, for
planning.
(4) For each solution, year of commissioning, short description of the basic technical
characteristics and the estimated value of investments must be presented.
Development plan for EPS
Article 58
(1) Based on the Strategic Plan, TSO is obliged each year to adopt and publish a transmission
development plan for a period of five years upon prior approval by Energy regulatory commission.
The plan should contain all necessary information to expand and upgrade of the system:
o Measures and investments for next five years,
o New connections of the transmission system users,
o Facilities envisaged for the reconstruction and revitalization,
o Estimating time and costs to build new objects for transmission system strengthening, and
o New interconnection lines with neighbouring EPS’s.
Investment plan for transmission system
Article 59
(1) Based on the Development Plan, TSO is obliged for each regulated period to adopt and publish
Investment Plan upon prior approval by Energy regulatory commission. The plan should emphasize
planned investments that reduce EE losses and improve quality of supplied EE from transmission
network.
II.9. Implementation
Solutions implementation
Article 60
(1) TSO is obliged to implement solutions according to the timeframe provided in the strategic and
development plan.

GRID CODE
29
(2) If defined solutions include changes in facilities, equipment and devices of users of the
transmission network, TSO reserves the right to impose such changes to the users of the
transmission network.
II.10. Evaluation of transmission network adequacy (ENTSO-E SAF)
Criteria
Article 45
(1) By assessing the reliability of electric power system, TSO determines whether the system can
meet the needs on the electricity market and market for reserves at any time in all connection
points and with acceptable standards.
(2) The evaluation of power system reliability is defined with two basic and functional criteria -
adequacy and security, where:
o The criterion of adequacy is applied to assess the ability of the EPS to supply the total needs
of EE and power, monitoring nominal and limit values of the system variables in different
regimes and taking into account planned and unexpected outages of system elements
o The criterion for security is applied to assess the ability of the EPS to withstand sudden
disturbances, or to withstand uncontrolled separation of the system in the case of major
disturbances.
(3) Adequacy of the EPS is a measure for ability of the system to supply consumers with EE in
normal operation regimes of the system, assuming the standard operating conditions and is
analysed over the adequacy of production and the adequacy of the transmission system:
o Adequacy of production is an assessment of the installed power in production comparing to
the total consumption of the EPS. Scope of the production adequacy forecast is to identify
possible problems and necessity for new production facilities, and
o Adequacy of the transmission system is an assessment of the network capacity necessary to
transmit power which is result of interaction between consumption and production. Scope of
the transmission system adequacy is to identify potential congestion and needs for
strengthening and construction of the new transmission lines.
(4) Indicators and methodology for analyses of the EPS and transmission network are defined in
APPENDIX 4 –TRANSMISSION SYSTEM ADEQUACY FORECAST.
Report form
Article 62
(1) Balance of EE and power referred to in Article 27 of these Code together with the results of
transmission capacities for analysed period referred to in Article 30 of these Code are displayed in
the form defined by ENTSO-E (APPENDIX 4 –TRANSMISSION SYSTEM ADEQUACY FORECAST), as
Forecast of System Adequacy - SAF (System Adequacy Forecast).

GRID CODE
30
III TRANSMISSION SYSTEM CONNECTION REQUIREMENTS
III.1 General
Article 63
(1) All facilities for generation, transmission, distribution and use of electricity must be properly
connected to the transmission network in order to avoid disruption of power system reliability.
(2) The requirements and obligations for connections to the transmission network given in this
Code are defined according to current technological achievements and recommendations of
ENTSO-E.
(3) The minimum requirements specified in Articles 36-40 of this Code that a consumer has to
meet in the procedure for connecting to the transmission network are considered as basic
requirements for connection and apply equally to all consumers.
III.2Objectives
Article 64
(1) Objective of the requirements for connection to the transmission system is to determine the
following:
o Minimum technical, conceptual and operational requirements that must be met by each
user connected to the transmission system, or any new user requesting connection
approval to the transmission system
o Minimum technical, conceptual and operational requirements that must be met by TSO,
related to the user’s connection point.
(2) Responsible parties for implementations of rules for connection to the transmission system are
TSO and transmission system users including the owners of interconnection lines subject to
exemption from provisions for transmission system access.
III.3 Connection Procedure
Procedure for connection to the transmission network
Article 65
(1) The procedure for connection to the transmission network consists of the following phases:
o submitting a request for approval to connect to the transmission network,
o preparation of a study for connection to the transmission network,
o issuing of an approval for connection to the transmission network,
o signing a contract for connection to the transmission network,
o approval of the project documentation,
o reporting for connection, compliance and testing (trial operation, testing and verification of
real and simulated dynamic response of the generator, adjusting the regulator and
protection, power quality etc.) and
o signing a contract for use of the transmission network.

GRID CODE
31
Documents for the procedure
Article 66
(1) TSO prepares the following documents in the process for connection:
o request form for approval to connect to the transmission network,
o a study for connection to the transmission network
o approval of the project documentation,
o decision for approving the connection to the transmission network,
o agreement for connection to the transmission network,
o reporting for connection, compliance and testing (reporting for equipment energizing,
periodical reporting on operation, reporting on constrained operation and final reporting for
operation)
 agreement to use the transmission network
Application for approval to connect to the transmission network
Article 67
(1) An applicant submits to the TSO the request for approval to connect to the transmission
network or change an existing connection in the initial phase of the planning for construction of a
facility for which should be provided a new/modified connection to the transmission network.
(2) The application must contain all the information needed to assess the connection, submitted
on a form prescribed by the TSO, which is available on the website of the TSO. (APPENDIX 5 –
APPLICATION FORM FOR CONNECTION APPROVAL).
Study of connection to the transmission network
Article 68
(1) TSO prepares the study for connection to the transmission network in which it assess the
impact on the reliability of the transmission network due to the connection and checks if the
requirements from the application for connection approval for the facility are met including the
choice of technical solution.
(2) In addition to the data in the application for connection to the transmission network, TSO may
further ask from the applicant other data which are necessary for the preparation of the study for
connection to the transmission network.
(3) The period for preparation of the study for connection to the transmission network cannot be
longer than 120 days after the submission of all data required by paragraph 2 of this Article. In
this period TSO and the applicant can further exchange technical data for the preparation of the
study.
(4) The study for connection to the transmission network includes:
o analysis of the technical solution for connection to the transmission network
o technical characteristics of the facility infrastructure and/or production unit,
o operational requirements for usage and

GRID CODE – RULES FOR ELECTRICAL TRANSMISSION SYSTEM OPERATION Macedonian Electrical Transmission System

GRID CODE – RULES FOR ELECTRICAL TRANSMISSION SYSTEM OPERATION Macedonian Electrical Transmission System

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GRID CODE – RULES FOR ELECTRICAL TRANSMISSION SYSTEM OPERATION Macedonian Electrical Transmission System