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©ABBPowerTechnology
1_114Q07-1-
Electrical
Diagrams
General
Single wire diagrams
©ABBPowerTechnology
1_114Q07-2-
AGENDA
 GENERAL
 SINGLE WIRE DIAGRAMS
 FUNCTIONAL DIAGRAMS
 WIRING DIAGRAMS
©ABBPowerTechnology
1_114Q07-3-
AGENDA
 GENERAL
 SINGLE WIRE DIAGRAMS
 FUNCTIONAL DIAGRAMS
 WIRING DIAGRAMS
©ABBPowerTechnology
1_114Q07-4-
General
 An electric diagram is a representation of how the different parts of
a network,...
©ABBPowerTechnology
1_114Q07-5-
 Functional: They also show the connections of the circuit
breakers (always in open posit...
©ABBPowerTechnology
1_114Q07-6-
 All collections of functional diagrams must show the conditions of
representation and no...
©ABBPowerTechnology
1_114Q07-7-
AGENDA
 GENERAL
 SINGLE WIRE DIAGRAMS
 Introduction
 Symbols
 Examples
 Single wire ...
©ABBPowerTechnology
1_114Q07-8-
Single-wire diagrams
 It is the representation in solely one line of
two or more conducto...
©ABBPowerTechnology
1_114Q07-9-
Single-wire diagrams
©ABBPowerTechnology
1_114Q07-10-
Single-wire diagrams
©ABBPowerTechnology
1_114Q07-11-
Single-wire diagrams
©ABBPowerTechnology
1_114Q07-12-
AGENDA
 GENERAL
 SINGLE WIRE DIAGRAMS
 Introduction
 Symbols
 Examples
 Single wire...
©ABBPowerTechnology
1_114Q07-13-
Symbols
Opened contact
Closed contact
Disconnector 89
Automatic circuit
breaker 52
©ABBPowerTechnology
1_114Q07-14-
Symbols
Current transformer
Current transformer
with marked polarity
One-phase voltage
tr...
©ABBPowerTechnology
1_114Q07-15-
Symbols
Thermal
relay [49]
Hour
counter
Ammeter
Voltmeter
Magneto-thermal
breaker [98]
Au...
©ABBPowerTechnology
1_114Q07-16-
Symbols
Integrator
Wattmeter
Active energy counter
Varmeter
Reactive energy counter
Synch...
©ABBPowerTechnology
1_114Q07-17-
Symbols
Three-winding three-phase
transformer
Three-winding three-phase
transformer
Three...
©ABBPowerTechnology
1_114Q07-18-
Standard device function number (IEEE C37.2)
©ABBPowerTechnology
1_114Q07-19-
AGENDA
 GENERAL
 SINGLE WIRE DIAGRAMS
 Introduction
 Symbols
 Examples
 Single wire...
©ABBPowerTechnology
1_114Q07-20-
Examples. Low voltage motor supply
 The following diagram shows the installation of
a th...
©ABBPowerTechnology
1_114Q07-21-
Examples. Low voltage motor supply
 The single-wire diagrams are
inadequate in diagrams ...
©ABBPowerTechnology
1_114Q07-22-
Examples. Outdoors MV transformation centre
©ABBPowerTechnology
1_114Q07-23-
Examples. Indoors MV transformation centre
1. Transformer bay.
2. Protection bay.
3. Inco...
©ABBPowerTechnology
1_114Q07-24-
AGENDA
 GENERAL
 SINGLE WIRE DIAGRAMS
 Introduction
 Symbols
 Examples
 Single wire...
©ABBPowerTechnology
1_114Q07-25-
Single-wire diagrams of transformer substations
 Symbols of circuit breakers
 Circuit b...
©ABBPowerTechnology
1_114Q07-26-
Single-wire diagrams of transformer substations
SYMBOL LABEL
Double side-break disconnect...
©ABBPowerTechnology
1_114Q07-27-
Single-wire diagrams of transformer substations
 Two disconnectors are
pictured: 89-5-1 ...
©ABBPowerTechnology
1_114Q07-28-
Single-wire diagrams of transformer substations
 Symbol of surge arresters
 Three Sieme...
©ABBPowerTechnology
1_114Q07-29-
Single-wire diagrams of transformer substations
 Symbols of power transformers
 Symbols...
©ABBPowerTechnology
1_114Q07-30-
Single-wire diagrams of transformer substations
 The specifications that should appear i...
©ABBPowerTechnology
1_114Q07-31-
Single-wire diagrams of transformer substations
 Transformer with:
 rated voltages 66 k...
©ABBPowerTechnology
1_114Q07-32-
Single-wire diagrams of transformer substations
 Current transformer symbols in accordan...
©ABBPowerTechnology
1_114Q07-33-
Single-wire diagrams of transformer substations
 Current transformer symbols
Fig. 20
Thr...
©ABBPowerTechnology
1_114Q07-34-
Single-wire diagrams of transformer substations
 Voltage transformer symbols
©ABBPowerTechnology
1_114Q07-35-
Single-wire diagrams of transformer substations
 Voltage transformer symbols
Fig. 25
Thr...
©ABBPowerTechnology
1_114Q07-36-
Single-wire diagrams of transformer substations
 Capacitive voltage divider symbol
 The...
©ABBPowerTechnology
1_114Q07-37-
Single-wire diagrams of transformer substations
 Capacitor battery
 Each capacitor has ...
©ABBPowerTechnology
1_114Q07-38-
Single-wire diagrams of transformer substations
 The measurement devices in any single-w...
©ABBPowerTechnology
1_114Q07-39-
Single-wire diagrams of transformer substations
 The protection relays in any single-wir...
©ABBPowerTechnology
1_114Q07-40-
 SW diagrams is the simplified description of the connections among the
different elemen...
©ABBPowerTechnology
1_114Q07-41-
 The most used bus bar arrangements are:
 Single bus
 Double bus
 Multiple bus
 Ring...
©ABBPowerTechnology
1_114Q07-42-
 The simplest arrangement is single bus
 Advantages:
 Simple and easy operation
 Very...
©ABBPowerTechnology
1_114Q07-43-
 “H” Diagram
 Particular case of split single bus with tie breaker or disconnector.
 V...
©ABBPowerTechnology
1_114Q07-44-
 The double bus conf. has several possibilities:
 One breaker, two disconnectors
 Brea...
©ABBPowerTechnology
1_114Q07-45-
 Breaker and a half:
 Solves the problem of breaker failure
 It complicates switching ...
©ABBPowerTechnology
1_114Q07-46-
 The ring arrangement rises reliability and flexibility
 It uses the same number of bre...
©ABBPowerTechnology
1_114Q07-47-
 In planning an electrical substation or switchyard facility, one should
consider major ...
©ABBPowerTechnology
1_114Q07-48-
AGENDA
 GENERAL
 SINGLE WIRE DIAGRAMS
 Introduction
 Symbols
 Examples
 Single wire...
©ABBPowerTechnology
1_114Q07-49-
General diagrams and their interpretation
 In these diagrams, besides
the power circuits...
©ABBPowerTechnology
1_114Q07-50-
General diagrams. Transformer bay
 The associated circuit breaker, 52-1, has the followi...
©ABBPowerTechnology
1_114Q07-51-
General diagrams. Transformer bay
 The circuit breaker receives tripping order from the ...
©ABBPowerTechnology
1_114Q07-52-
General diagrams. Transformer bay
 86: Receives tripping order from the operation of the...
©ABBPowerTechnology
1_114Q07-53-
General diagrams. Transformer bay
 86: Receives tripping order from the operation of the...
©ABBPowerTechnology
1_114Q07-54-
General diagrams. Bus voltage transformer
©ABBPowerTechnology
1_114Q07-55-
 The secondary windings of the voltage transformers are protected by
automatic circuit b...
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Electrical diagrams1

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Electrical diagrams1

  1. 1. ©ABBPowerTechnology 1_114Q07-1- Electrical Diagrams General Single wire diagrams
  2. 2. ©ABBPowerTechnology 1_114Q07-2- AGENDA  GENERAL  SINGLE WIRE DIAGRAMS  FUNCTIONAL DIAGRAMS  WIRING DIAGRAMS
  3. 3. ©ABBPowerTechnology 1_114Q07-3- AGENDA  GENERAL  SINGLE WIRE DIAGRAMS  FUNCTIONAL DIAGRAMS  WIRING DIAGRAMS
  4. 4. ©ABBPowerTechnology 1_114Q07-4- General  An electric diagram is a representation of how the different parts of a network, an installation, or a device (or group of devices) are connected and related among them.  The diagrams are classified in:  Single-wire: These diagrams show the path of current circulation, as well as the main elements of the power system (lines, buses, transformers, circuit breakers, disconnectors, surge arresters, generator, etc.).  They show solely one phase of the circuit in balanced systems.  Multiwire: They are more complete than single-wire diagrams, since they present the information of every phase of the circuit.
  5. 5. ©ABBPowerTechnology 1_114Q07-5-  Functional: They also show the connections of the circuit breakers (always in open position), disconnectors (also in open position), AC and DC circuits without voltage, unexcited auxiliary relays, open AC and DC circuit breakers, signal and drive switches, etc.  Wiring: There are two kinds of wiring diagrams:  Interconnection among devices.  Internal interconnection of devices.  When elaborating a diagram, care should be taken to make it as easy to understand as possible, avoiding information that could lead to confusion. General
  6. 6. ©ABBPowerTechnology 1_114Q07-6-  All collections of functional diagrams must show the conditions of representation and nomenclature of terminals, as following:  Conditions of representation of diagrams:  Open circuit breakers. Unloaded springs.  Open disconnectors.  Unloaded AC and DC circuits.  Unexcited auxiliary relays.  Open AC and DC automatic circuit breakers.  Signal and drive switches in position “rest after opening”.  Terminal nomenclature  Position switchboard, frontal.  Position switchboard, back.  Other switchboards.  Outdoors devices and boxes. General
  7. 7. ©ABBPowerTechnology 1_114Q07-7- AGENDA  GENERAL  SINGLE WIRE DIAGRAMS  Introduction  Symbols  Examples  Single wire diagrams of transformer substations  General diagrams and their interpretation  FUNCTIONAL DIAGRAMS  WIRING DIAGRAMS
  8. 8. ©ABBPowerTechnology 1_114Q07-8- Single-wire diagrams  It is the representation in solely one line of two or more conductors.  Hence, it might represent:  Circuits of one-phase or multi-phase systems  Conductors with the same layout.  The line that symbolizes the conductors of a sole circuit will be crossed by as many diagonal lines as phases are in the circuit. This criterion is not applied to high voltage installations.  The single-wire diagrams can be:  General  Simplified  The difference between them resides in the level of detail, minor in the seconds.
  9. 9. ©ABBPowerTechnology 1_114Q07-9- Single-wire diagrams
  10. 10. ©ABBPowerTechnology 1_114Q07-10- Single-wire diagrams
  11. 11. ©ABBPowerTechnology 1_114Q07-11- Single-wire diagrams
  12. 12. ©ABBPowerTechnology 1_114Q07-12- AGENDA  GENERAL  SINGLE WIRE DIAGRAMS  Introduction  Symbols  Examples  Single wire diagrams of transformer substations  General diagrams and their interpretation  FUNCTIONAL DIAGRAMS  WIRING DIAGRAMS
  13. 13. ©ABBPowerTechnology 1_114Q07-13- Symbols Opened contact Closed contact Disconnector 89 Automatic circuit breaker 52
  14. 14. ©ABBPowerTechnology 1_114Q07-14- Symbols Current transformer Current transformer with marked polarity One-phase voltage transformer Voltage transformer with marked polarity One-phase voltage transformer
  15. 15. ©ABBPowerTechnology 1_114Q07-15- Symbols Thermal relay [49] Hour counter Ammeter Voltmeter Magneto-thermal breaker [98] Auxiliary relay coil Tilting auxiliary relay Time-delay relay coil
  16. 16. ©ABBPowerTechnology 1_114Q07-16- Symbols Integrator Wattmeter Active energy counter Varmeter Reactive energy counter Synchronoscope Display Frequency meter Current converter Voltage converter Active power converter
  17. 17. ©ABBPowerTechnology 1_114Q07-17- Symbols Three-winding three-phase transformer Three-winding three-phase transformer Three-phase transformer of multiple taps with on-load tap changer
  18. 18. ©ABBPowerTechnology 1_114Q07-18- Standard device function number (IEEE C37.2)
  19. 19. ©ABBPowerTechnology 1_114Q07-19- AGENDA  GENERAL  SINGLE WIRE DIAGRAMS  Introduction  Symbols  Examples  Single wire diagrams of transformer substations  General diagrams and their interpretation  FUNCTIONAL DIAGRAMS  WIRING DIAGRAMS
  20. 20. ©ABBPowerTechnology 1_114Q07-20- Examples. Low voltage motor supply  The following diagram shows the installation of a three-phase motor, with tripolar circuit breaker and three protection fuses.  The representative conductor is crossed by three diagonal lines, showing that this is a three-phase circuit.  The terminals of the fuses of each phase are indicated (1-2, 3-4 and 5-6), as well as those of the poles of each phase of the circuit breaker.  There had not been indicated the characteristics of the installation, such as rated voltage, conductors section, motor power, or fuses and circuit breaker characteristics.
  21. 21. ©ABBPowerTechnology 1_114Q07-21- Examples. Low voltage motor supply  The single-wire diagrams are inadequate in diagrams of motor installation when they have the possibility of turn inverter, stator-resistances starter, speed variation, etc.  In these cases, the multiwire diagram is recommended, as shown in Fig.  It can be appreciated the circuit breaker Q1, two contactors KM1 and KM2 to invert the direction of rotation, a contactor KM11 to short- circuit the resistances and the three-phase motor.
  22. 22. ©ABBPowerTechnology 1_114Q07-22- Examples. Outdoors MV transformation centre
  23. 23. ©ABBPowerTechnology 1_114Q07-23- Examples. Indoors MV transformation centre 1. Transformer bay. 2. Protection bay. 3. Incoming feeder bay. 4. Outgoing feeder bay. 5. Low voltage switchboard. MAIN BUS OUTGOING FEEDERS LOW VOLTAGE SWITCHBOARD CIRCUIT BREAKER TRIPOLAR DISCONNECTOR GROUNDING TRANSFORMER FUSE MULTIPOLAR CIRCUIT BREAKER TERMINAL
  24. 24. ©ABBPowerTechnology 1_114Q07-24- AGENDA  GENERAL  SINGLE WIRE DIAGRAMS  Introduction  Symbols  Examples  Single wire diagrams of transformer substations  General diagrams and their interpretation  FUNCTIONAL DIAGRAMS  WIRING DIAGRAMS
  25. 25. ©ABBPowerTechnology 1_114Q07-25- Single-wire diagrams of transformer substations  Symbols of circuit breakers  Circuit breaker of the manufacturer AEG,  rated voltage 72.5 kV,  rated current 1250 A  breaking capacity of 25 kA.  Besides, it is indicated as the circuit breaker number 5 of the 72.5 kV switchyard.
  26. 26. ©ABBPowerTechnology 1_114Q07-26- Single-wire diagrams of transformer substations SYMBOL LABEL Double side-break disconnectors Centre-break disconnectors Pantograph disconnectors General symbol (unipolar disconnector)  Symbols of disconnectors
  27. 27. ©ABBPowerTechnology 1_114Q07-27- Single-wire diagrams of transformer substations  Two disconnectors are pictured: 89-5-1 and 89-5-2.  Both have the same characteristics:  Model: MESA "SGC".  Rated voltage: 72.5 kV.  Rated current: 1250 A.
  28. 28. ©ABBPowerTechnology 1_114Q07-28- Single-wire diagrams of transformer substations  Symbol of surge arresters  Three Siemens surge arresters,  model EP2060-2PN  rated voltage 60 kV,  star-connected and grounded.  It has not been indicated the model of the installed discharge counter.
  29. 29. ©ABBPowerTechnology 1_114Q07-29- Single-wire diagrams of transformer substations  Symbols of power transformers  Symbols of autotransformers
  30. 30. ©ABBPowerTechnology 1_114Q07-30- Single-wire diagrams of transformer substations  The specifications that should appear in the diagrams for these equipments are:  The transformers are signalled by the letter T followed by the number that indicates their order inside the substation where they are installed.  The autotransformers are signalled by the letters AT followed by the number that indicates their order inside the substation where they are installed.  Power expressed in MVA or kVA.  Connection group.  Rated voltage of every winding.  Indication of the grounding connection.
  31. 31. ©ABBPowerTechnology 1_114Q07-31- Single-wire diagrams of transformer substations  Transformer with:  rated voltages 66 kV and 50 kV in the high voltage side  22 kV in the secondary  on-load tap changer, as indicated by the arrow that crosses the primary winding.  The voltage of operation is indicated by underlining.  In the transformers with no- load tap changer the following symbol is utilised:
  32. 32. ©ABBPowerTechnology 1_114Q07-32- Single-wire diagrams of transformer substations  Current transformer symbols in accordance to different standards
  33. 33. ©ABBPowerTechnology 1_114Q07-33- Single-wire diagrams of transformer substations  Current transformer symbols Fig. 20 Three transformers, manufacturer Arteche, model CXG-72, transforma- tion ratio, delta-connected. Fig. 21 Three current transformers, bushing type BM, mounted inside a circuit breaker.
  34. 34. ©ABBPowerTechnology 1_114Q07-34- Single-wire diagrams of transformer substations  Voltage transformer symbols
  35. 35. ©ABBPowerTechnology 1_114Q07-35- Single-wire diagrams of transformer substations  Voltage transformer symbols Fig. 25 Three one-phase voltage transformers removable type with double secondary winding: - One star-connected. - The other connected in open delta. - The primary is star- connected and pro- tected with fuses.
  36. 36. ©ABBPowerTechnology 1_114Q07-36- Single-wire diagrams of transformer substations  Capacitive voltage divider symbol  The diagram also shows the equipment of the drainage coil, connected in parallel with a discharger and a disconnector, so when the drainage coil has to be disconnected the ground reference in the capacitive divider is not lost.
  37. 37. ©ABBPowerTechnology 1_114Q07-37- Single-wire diagrams of transformer substations  Capacitor battery  Each capacitor has individual protection (fuses).  The battery has an installed power of 3600 kVAr, is star-connected and fed by an underground cable with a rated voltage of 22/ kV.  It also includes three voltage transformers for measurement and protection.
  38. 38. ©ABBPowerTechnology 1_114Q07-38- Single-wire diagrams of transformer substations  The measurement devices in any single-wire diagram are represented by a circle, including their correspondent symbol: - Voltmeter - Ammeter - Wattmeter
  39. 39. ©ABBPowerTechnology 1_114Q07-39- Single-wire diagrams of transformer substations  The protection relays in any single-wire diagram are represented by a circle, including their correspondent number, according to standard IEEE C37.2-1996: Synchronism-check device Distance relay Differential protective relay
  40. 40. ©ABBPowerTechnology 1_114Q07-40-  SW diagrams is the simplified description of the connections among the different elements in a substation  It is defined by :  Nº of transformers  Nº source and feeder lines  Buses configuration  Switching elements 220 kV L1 EB L2 L3 L4 T1 T2 T3 MT 10L - - - EB1 10L - - - EB2 10L - - - 50MVA 50MVA 50MVA PB Single-wire diagrams of transformer substations
  41. 41. ©ABBPowerTechnology 1_114Q07-41-  The most used bus bar arrangements are:  Single bus  Double bus  Multiple bus  Ring bus  Every bay is composed by several elements:  When the breakers are detachable it is not necessary to install isolating disconnectors Isolating Disconnector By- pass Disconnector (optional) Breaker Single-wire diagrams of transformer substations
  42. 42. ©ABBPowerTechnology 1_114Q07-42-  The simplest arrangement is single bus  Advantages:  Simple and easy operation  Very easy interconnection wiring  Reduced cost  Disadvantages:  A single bus failure implies substation blackout  Breaker maintenance implies bay outage (by-pass)  ST expansion needs de-energizing  Reliability can be improved splitting the bus and/or adding by pass disconnectors for maintenance purposes ......... ....... ...... ...... Single-wire diagrams of transformer substations
  43. 43. ©ABBPowerTechnology 1_114Q07-43-  “H” Diagram  Particular case of split single bus with tie breaker or disconnector.  Very used in distribution or customer substations  Two possibilities, H3 (3 breaker) or H4 (4 breaker) ...... ...... ...... ...... Single-wire diagrams of transformer substations
  44. 44. ©ABBPowerTechnology 1_114Q07-44-  The double bus conf. has several possibilities:  One breaker, two disconnectors  Breaker and a half  Two breakers  Advantages:  Flexibility for circuits clustering  Bus maintenance without de-energizing  Disadvantages:  More area needed. Higher cost  Breaker failure implies circuit outage  Reliability is improved with bus tie breaker:  Load transfer  Line breaker outage ......... ......... Single-wire diagrams of transformer substations
  45. 45. ©ABBPowerTechnology 1_114Q07-45-  Breaker and a half:  Solves the problem of breaker failure  It complicates switching and protection  Higher cost and area needs  Two breakers:  Greater flexibility  Greater reliability  Higher cost and area needs ............ ............ Single-wire diagrams of transformer substations
  46. 46. ©ABBPowerTechnology 1_114Q07-46-  The ring arrangement rises reliability and flexibility  It uses the same number of breakers than circuits  Advantages:  Breaker disconnection does not imply outage  Two sources for every circuit  Disadvantages:  More complicated operation  More complex protections  Expansion limited Single-wire diagrams of transformer substations
  47. 47. ©ABBPowerTechnology 1_114Q07-47-  In planning an electrical substation or switchyard facility, one should consider major parameters as discussed,  Reliability  Cost  Available area  Most used arrangements:  Transmission substation, double bus generally  Distribution substations,  Single bus in HV (H3- H4)  Double bus in MV  Customer substation  Single bus in HV (H3, H4) Single-wire diagrams of transformer substations
  48. 48. ©ABBPowerTechnology 1_114Q07-48- AGENDA  GENERAL  SINGLE WIRE DIAGRAMS  Introduction  Symbols  Examples  Single wire diagrams of transformer substations  General diagrams and their interpretation  FUNCTIONAL DIAGRAMS  WIRING DIAGRAMS
  49. 49. ©ABBPowerTechnology 1_114Q07-49- General diagrams and their interpretation  In these diagrams, besides the power circuits, the circuits of protection and measurement are also included.  The characteristics of all represented devices (transformers, capacitor batteries, etc.) shall be indicated, including protection relays and automatisms.
  50. 50. ©ABBPowerTechnology 1_114Q07-50- General diagrams. Transformer bay  The associated circuit breaker, 52-1, has the following characteristics:  Manufacturer: Sprecher.  Model: HPF-409H  Rated voltage: 72.5 kV.  Rated current: 1600 A.  Breaking capacity: 20 kA.
  51. 51. ©ABBPowerTechnology 1_114Q07-51- General diagrams. Transformer bay  The circuit breaker receives tripping order from the following relays:  51: Direct order.  86: Receives tripping order from the operation of the relays:
  52. 52. ©ABBPowerTechnology 1_114Q07-52- General diagrams. Transformer bay  86: Receives tripping order from the operation of the relays:  87: Differential.  63B: Buchholz relay of pressure of the liquid of the transformer. Provides alarm and tripping for the circuit breaker 52-1 through the relay 86 and by means of its auxiliary 63BX.
  53. 53. ©ABBPowerTechnology 1_114Q07-53- General diagrams. Transformer bay  86: Receives tripping order from the operation of the relays:  51NX: Actuates as a consequence of the operation of the relay 51N of neutral overcurrent, also providing the corresponding alarm. The 51N relay is fed by a current transformer type BR, with ratio 300/5 A, power 15 VA and class S20 that trips over circuit breaker 52-6.  50: Instantaneous overcurrent relays fed by current transformers type BR, with ratio 300/5 A, power 15 VA and class S20.  63N: Pressure indicator relay of the liquid where the reactance TZ-1 is immersed. This relay 63N trips the relay 86 by means of its auxiliary 63NX, raising the corresponding alarm by the relay 63AX.  26: Thermal relay of overtemperature indication of the liquid where the reactance TZ-1 is immersed. It provides alarm indication but no tripping order over the circuit breaker.
  54. 54. ©ABBPowerTechnology 1_114Q07-54- General diagrams. Bus voltage transformer
  55. 55. ©ABBPowerTechnology 1_114Q07-55-  The secondary windings of the voltage transformers are protected by automatic circuit breakers 98. The 98 in the star-connected secondary winding of voltage 0.11/ kV activates an auxiliary relay 98X. From this winding, the bus voltage measurement is obtained by means of a voltmeter of 0-75 kV connected through a voltage switch CV. Three fuses of 2 A had been installed to protect the voltmeter.  The diagram also represents a frequency automatism by the utilization of a frequency relay 81 that by means of the auxiliary relay 81X causes the automatic closing of the general circuit breakers of 22 kV.  However, the relay 81Y, auxiliary of 81, is the one to trip the general circuit breakers of 22 kV. The frequency automatism is activated by the operation of the switch 69F.  There is installed as well an automatism for the automatic reposition of voltage, for which a relay 27B has been installed, fed by the star- connected secondary winding of voltage 0.11/ kV. The auxiliary relays 27BX, 94-1 and 94-2 of the relay 27B trip the lines L-1 and L-2. General diagrams. Bus voltage transformer

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