Study on Excitation system in Power sector

WELCOME TO THE INTRODUCTION ON
STATIC EXCITATION SYSTEM
Study by Boben Anto C

TOPICS
SL.NO DESCRIPTION
1 INTRODUCTION
2 ROLE OF EXCITATION SYSTEM
3 TYPES OF EXCITATION SYSTEM
4 CONSTRUCTION OF STATIC EXCITATION SYSTEM
5 START UP METHOD OF EXCITATION SYSTEM
6 FUNCTION OF AUTO AND MANUAL CHANNELS
7 IMPORTANCE OF EXCITATION SYSTEM
8 EFFECTS OF EXCITATION SYSTEM ON TRANSIENT STABILITY
9 RETROFITTING OF SES

ELECTRICAL ENERGY IS THE PUREST FORM OF ENERGY IN
FLEXIBILITY OF
• GENERATION
• TRANSMISSION AND DISTRIBUTION
• AND UTILISATION
• ELECTRICAL POWER IS GENERATED BY SYNCHRONOUS
MACHINES
• OUR SYNCHRONOUS GENERATORS WORK UNDER THE
PRINCIPLE OF FARADAY
,
S LAW OF ELECTROMAGNETIC
INDUCTION
FARADAY
,
S LAW OF ELECTROMAGNETIC INDUCTION
E.M.F α N X dФ/dt
INTRODUCTION-I

INTRODUCTION-II
 According to Faraday’s Law of Electromagnetic Induction the
following 3 things are essential for the generation of e.m.f
1. Electrical Conductor- STATOR WINDING.
2. Magnetic Field- FIELD WINDING-ROTOR.
RELATIVE MOTION BETWEEN THESE TWO WHICH IS
ACHIEVED BY THE
3. Prime Mover-TURBINE.

ROLE OF EXCITATION SYSTEMS
• THE MAIN FUNCTION OF EXCITATION SYSTEMS IS TO FEED
DC VOLTAGE TO THE ROTOR WINDINGS TO GENERATE THE
MAGNETIC FIELD ACCORDING TO THE OPERATING
CONDITIONS.
• EXCITATION CONTROL SYSTEMS HAVE BEEN UNDERGOING
IMPROVEMENTS/ MODIFICATIONS IN LINE WITH LARGER AND
COMPLEX POWER SYSTEM.

OBJECTIVES OF STATIC EXCITATION SYSTEM
MAINLY TO MAINTAIN THE TERMINAL VOLTAGE OF A GENERATOR AT
A PREDETERMINED VALUE,
INDEPENDENT OF THE CHANGE IN LOADING CONDITIONS.
IN ADDITION TO THIS,THE EXCITATION SYSTEM HAS TO CONTRIBUTE
THE FOLLOWING FUNCTIONS ALSO.
1. MAINTENANCE OF STABLE OPERATION OF MACHINE UNDER STEADY
STATE, TRANSIENT AND DYNAMIC CONDITIONS.
2. EFFECTIVE UTILIZATION OF MACHINE CAPABILITIES WITHOUT
EXCEEDING MACHINE OPERATING LIMITS,(USING LIMITERS)
3. SATISFACTORY OPERATION WITH OTHER MACHINES CONNECTED IN
PARALLEL ( MVAR CONTROL)
Study of Boben Anto C

TYPES OF EXCITATION SYSTEM
AT PRESENT VARIOUS TYPES OF EXCITATION SYSTEMS ARE
AVAILABLE SUCH AS,
1. CONVENTIONAL DC-GENERATOR T.G SHAFT MOUNTED
2.HIGH FREQUENCY AC GENERATOR-RECTIFIER
3. STATIC EXCITATION
4 BRUSHLESS-EXCITATION-WITH ROTATING DIODES
 BASED ON THE TYPE OF SOURCE,THIS CAN BE FURTHER CLASSIFIED
AS,
1. SHUNT / SELF EXCITATION / DIRECT
2. SEPARATELY / INDIRECTLY EXCITED SYSTEM
 BASED ON THE CONTROL PHILOSOPHY,
1. ELECROMECHANICAL
2. STATIC ANALOG.
3. DIGITAL/NUMERICAL.

GENERATOR CAPABILITY CHART

FUNCTIONS OF STATIC EXCITATION SYSTEM
1. THE CAPABILITY DIAGRAM OF GENERATOR SHOWN GIVES THE SAFE
OPERATING REGIMES AND LIMITATIONS OF THE MACHINE.
2. THE LIMIT CONTROLLERS IN EXCITATION SYSTEM ARE SET
ACCORDINGLY TO ACT ON BOTH THE LAGGING AND LEADING SIDES IN
THE CAPACITY DIAGRAM.
3. THIS PREVENT UNNECESSARY TRIPPING BY KEEPING THE MACHINE
WELL WITHIN THE SAFE LIMITS.
4. THE LIMIT CONTROLLERS DO NOT REPLACE THE FUNCTION OF
PROTECTIVE RELAYS BUT ENHANCE THE STABILITY OF THE MACHINE,
THEREBY INCREASING ITS AVAILABILITY TO THE NETWORK.
5. THE POWER SYSTEM STABILIZER IN EXCITATION IMPROVES THE
DYNAMIC STABILITY, THE OPERATING RANGE OF GENERATOR BUT
ALSO THE STABILITY OF INTERCONNECTED SYSTEMS.

LIMITERS IN SES
The following limiters keep the Generator operating well within
the capability limit
1. STATOR CURRENT LIMITER( LAG AND LEAD)
2. OVER EXCITATION ROTOR CURRENT LIMITER
3. UNDER EXCITATION ROTOR CURRENT LIMITER
4. LOAD ANGLE LIMITER
5. GT OVER FLUX LIMITER
6. POWER SYSTEM STABILIZER

EXCITATION SYSTEM -REQUIREMENTS
IN ORDER TO MAINTAIN SYSTEM STABILITY
1. FAST ACTING –GOOD RESPONSE TIME
2. ACCURACY TO MATCH
3. STABILITY
a) STEADY STATE
b) TRANSIENT
TO VARY THE FIELD CURRENT EXTREMELY FAST TO THE
CHANGING OPERATIONAL TRANSIENT CONDITIONS.
IT IS BECAUSE OF THESE REASONS, THE DIGITAL
EXCITATION SYSTEM IS PREFERRED OVER STATIC
EXCITATION SYSTEM.

DIFFERENT PARTS OF SES
1. EXCITATION
TRANSFORMER
2. THYRISTOR BRIDGES
3. FIELD BREAKER with
discharge circuits
4. FIELD FLASHING
EQUIPMENTS
POWER
CONTROL
1. AVR ,FCR
CIRCUITS /
RELAYS
2. ELECTRONIC
CARDS

CONSTRUCTION OF STATIC EXCITATION SYSTEM-II
TO ACHIEVE THESE RATED PARAMETERS, THE POWER STAGE OF
EXCITATION SYSTEM CONSISTS OF
1. SIX THYRISTOR BRIDGES (EACH BRIDGE IS 1000A CAPACITY) WITH
100% REDUNDANCY.
2. THESE BRIDGES, WORKING IN PARALLEL CONVERT THE AC
VOLTAGE SUPPLIED FROM EXCITATION TRANSFORMER INTO
VARIABLE DC VOLTAGE.
3. THIS IS FED TO THE FIELD THROUGH FIELD BREAKER.
4. FIELD DISCHARGE CIRCUIT HELPS TO DISCHARGE THE RESIDUAL
FIELD ENERGY TO AVOID ROTOR OVER VOLTAGE.
5. ROTOR OVER VOLTAGE WILL OCCUR AT THE TIME OF TRIPPING /
OPENING OF FIELD BREAKER / DURING ASYNCHRONOUS
OPERATION.
IN EXCITATION SYSTEM TWO CONTROL CHANNELS ARE AVAILABLE
NAMELY AUTO CHANNEL
MANUAL CHANNEL Study by Boben Anto C

CONSTRUCTION OF STATIC EXCITATION SYSTEM-I
In Static Excitation system,
The generator output voltage / reactive power is controlled .
1. The Excitation power is tapped off from the generator terminal,
2. V G is Stepped down by excitation transformer,
3. Rectified by FULLY CONTROLLED Thyristor bridges and then
4. Fed to the generator field through FB ,Brush gear and sliprings .
5. A high control speed is achieved by using an inertia free control and power
electronic system.
The excitation system rated parameters are,
Rated Field voltage Vf = 340 V DC (STAGE-I) / 310 V DC ( STAGE-II)
Rated Field current If = 2854 A (STAGE-I) / 2600 A (STAGE-II)

START UP METHOD OF EXCITATION SYSTEM
1. FOR THE INITIAL BUILD-UP OF THE GENERATOR VOLTAGE A
FIELD FLASHING EQUIPMENT IS REQUIRED IN SHUNT EXCITATION
SYSTEM.
2. THE FIELD FLASHING CIRCUIT INITIALLY SUPPLIES THE STANDBY
DC VOLTAGE TO THE FIELD OF THE GENERATOR FOR A SHORT
PERIOD.
3. WHEN THE GENERATOR TERMINAL VOLTAGE REACHES 30% OF
THE RATED VALUE, THE FIRING PULSES ARE RELEASED TO THE
THYRISTORS.
4. AT THE TIME OF REACHING ITS 70% OF RATED VALUE, THE FIELD
FLASHING SUPPLY IS ISOLATED AUTOMATICALLY & SWITCHING
OVER THE CONTROL COMPLETELY TO THE THYRISTOR BRIDGES
THERE AFTER.

STATIC EXCITATION SYSTEM BLOCK DIAGRAM

FUNCTION OF AUTO AND MANUAL CONTROLS-I
1. AUTO CHANNEL IS A CLOSED LOOP CONTROL SYSTEM(PID)
2. MANUALCHANNEL IS OPEN LOOP CONTROL SYSTEM WHICH IS
BACK-UP FOR AUTO CHANNEL.(PI)
3. IN AUTO CHANNEL, THE VOLTAGE REGULATOR HAVING CLOSE
LOOP CONTROLS
4. IT COMPARES THE ACTUAL TERMINAL VOLTAGE OF THE MACHINE
WITH THE SET REFERENCE VALUE AND FORMS AN ERROR SIGNAL.
5. THIS CAUSES THE VOLTAGE REGULATOR TO ADVANCE OR RETARD
THE FIRING ANGLE OF THE THYRISTOR BRIDGES THEREBY
CONTROLLING THE FIELD EXCITATION OF THE GENERATOR.

1. THE AUTO AND MANUAL CHANNELS HAVE SEPARATE FIRING PULSE
GENERATING CIRCUITS, WHICH CONTROL THE THYRISTOR BRIDGES
ACCORDING TO THE SELECTION.
2. THE FIRING PULSE GENERATOR USES THE CONTROL VOLTAGE AND
THE SYNCHRONIZING VOLTAGE, WHICH IS OBTAINED FROM
SYNCHRONIZING TRANSFORMER TO GENERATE SIX SETS OF PULSES
IN CORRECT SEQUENCE.
3. ACCORDING TO THE CONTROL MODE SELECTED EITHER AUTO OR
MANUAL, THE CORRESPONDING FIRING PULSES WILL BE RELEASED
TO THE THYRISTORS.
4. THE OTHER SET OF PULSES WILL BE TRACKING THE RELEASED
PULSES. (FOLLOWUP CIRCUITS)
5. THIS IS TO HAVE A SMOOTH CHANGE OVER WITHOUT VARYING THE
GENERATOR TERMINAL VOLTAGE WHEN THE CONTROL MODE IS
CHANGED.
FUNCTION OF AUTO AND MANUAL CONTROLS-II

EFFECTS OF EXCITATION SYSTEM ON TRANSIENT STABILITY-I
1. SINCE THE TRANSIENT STABILITY PROBLEMS DEAL WITH THE
PERFORMANCE OF POWER SYSTEM WHEN SUBJECTED TO SUDDEN
DISTURBANCES SOMETIMES LEADING TO LOSS OF SYNCHRONISM. (POLE
SLIPPING)
2. THE MAJOR FACTOR INFLUENCING THIS CONDITION ARE THE MACHINE
BEHAVIOR AND THE POWER NETWORK DYNAMIC RELATIONS.
3. IT IS ASSUMED THAT THE MECHANICAL POWER SUPPLIED BY THE PRIME
MOVERS REMAINS CONSTANT DURING THE DISTURBANCE.
4. THE EFFECT OF EXCITATION CONTROL ON THOSE TYPE OF TRANSIENT
DEPENDS ON ITS ABILITY TO HELP THE GENERATORS TO MAINTAIN ITS
OUTPUT POWER IN THE ABOVE PERIOD.

RETROFITTING OF SES
WHEN ?
1. OEM STOPS SUPPLYING THE SPARES.
2. SYSTEM BECOMES UNRELIABLE DUE TO AGEING DESPITE
PROPER MAINTENANCE
3. O&M COST BECOMES HIGHER AND HIGHER.

RETROFITTING OF SES-BENEFITS
ADVANTAGES ADOPTING THE LATEST TECHNOLOGY.
1. MINIMUM COMPONENTS.
2. BETTER AND RELIABLE PERFORMANCE.
3. MORE LIFE EXPECTANCY.
4. LESS MAINTENANCE.
5. EASY INTERFACE WITH HIGHER LEVEL AUTOMATION LIKE DCS.

FEATURES OF SES-NEW Retrofit (CASE-1)
• FAST RESPONSE < 20 m seconds.
• BETTER CONTROL ACCURACY.
• MORE USER FRIENDLY CONTROL.
• MORE FLEXIBLITY IN PARAMETER SETTING.
• EASY MAINTENANCE ACCESS.
• MINIMUM SPARES.
• MINIMUM COMMISSIONING TIME USING CMT TOOLS.

OVERVIEW OF SES-NEW
• ABB‟s UNITROL 5000 MODEL
• 2 REDUNTANT AVR CHANNELS BOTH HAVING MANUAL BACKUP.
• 4 THYRISTOR BRIDGES [Each 2000 A] .
• AUTOMATIC EQUAL CURRENT SHARING AMONG THYRISTOR
BRIDGES.
• DIGITALLY CONTROLLED PROGRAMMABLE TYPE.
• SELF DIAGNOSTATICS FEATURE.
• FAULT HISTORY WITH REAL TIME STAMPING AND TRENDING.

Automatic Voltage Regulator
VOLTAGE VARIATION DUE TO
• LOAD (IR) DROP
• ARMATURE REACTION

FUNCTIONS OF AVR
• To maintain the constant generator terminal voltage
• Meet excitation power requirements under all normal operating
conditions
• Improve dynamic and transient stability thereby increasing
plant/machine availability
• Regulate MVAR loading with in limits

COMPONENTS OF AVR
• CONTROL AMPLIFIER - UN 2010 MODULE
• INPUT CIRCUITS- 3 PHASE VOLTAGE-110 V AC
• 3 PHASE CURRENT 1A OR 5A
• A Circuitry is available in the module for adding the current
signals VECTORIALY to the voltage signals for providing
compensation as a function of active or reactive power flowing
in the generator terminals.

• Actual value converting unit
• A voltage proportional to frequency network which reduces the
excitation current when frequency falls below the set level, thus
keeping the air gap flux constant. This prevents saturation of
connected transformers and possible over voltage.
• Reference value circuit - temperature compensated zener diode
90-110% of gen. Terminal voltage
• Control amplifier-compares measured value and ref. Value -
output deviation
• Accepts other signals from various limiters, power system
stabilizer

VG = kf where, k is a constant
f is the frequency
In order for the excitation current to remain constant while the
generator voltage is following the above relation, the sensing
voltage must be kept constant.
In the circuit,
Voltage across the capacitor VC = IC.XC
where, XC = 1/C
IC = IR/3
IR = VG
1/R3
IC = VG
1/R3
substituting VC = IC.XC
= (VG
1/3R).(1/C)
= VG
1/3RC
= VG
1/6fRC where =2f

where VG
1 =(VGN
1/fN).f
where VGN
1 = rated sensing voltage
fN = rated frequency
VGN
1 . f VGN
1
VC = ----------------- = 6.fN.R.C
6.fN.f.R.C
VGN
1
VC = -------------
6 fn. R. C.
It can be seen that for the condition
R >> 1/C and VG = k . f, the voltage Vc is constant.
The voltage Vc is then fed to the rectifier bridge.

PID CONTROLLER
• The objective of any closed loop control system is to keep the
following parameters in check.
 The overshoot after any step change in controlled variable (in
this case the voltage) should be within acceptable limits for the
system to be stable.
 The response time should be as small as possible so that the
corrective action to any change in the controlled variable is taken
by the controller without any appreciable lapse of time
• Steady state error should be as small as possible

PID CONTROLLER
 The settling time should be as small as possible
 The system should remain stable for a wide range of operating points.
 It is not possible for the control amplifier alone to take care of all said
points.
• Hence to improve the performance compensation networks are
provided in the control amplifier.
• These compensation networks are namely PROPORATIONAL,
INTEGRAL AND DERIVATIVE feed back circuits.

LIMIT CONTROLLERS
• With ever increasing size of generating units today, more
stringent requirements have to be met by excitation systems.
• Static Excitation assures, stable operation both under dynamic
and transient conditions
• Generators running in parallel with the power network even under
extreme conditions must remain in synchronism without the
maximum load limit on it being exceeded and without the
protective relays operating.
• An automatic voltage regulator AVR alone cannot ensure this.
• Optimum utilization of the generator can be ensured only if the
basic AVR is influenced by additional signals to limit the under-
excitation and over-excitation of the machine.

LIMIT CONTROLLERS
Thus, limit controllers working in conjunction with the AVR
ensure :
• Optimum utilization of the machine.
• Security of parallel operation etc.

LIMIT CONTROLLERS
• Limit controllers simplify the job of the operating-staff
• Enables stable operation close to the limiting values.
• With limit controllers in service, operational errors and faults
in the regulator lead only to the limit value control and not to
disconnection.

LIMIT CONTROLLERS
• Limit controllers are not meant to replace the protection
system.
• They are intended to prevent the protection system from
operating under extreme transient conditions.

LIMIT CONTROLLERS
• Limiters, whenever they intervene, influence the voltage
regulator suitable to bring about a corresponding change in the
excitation.
• The following are the parameters which are to be limited.
– Stator current under condition of over Excitation and under
excitation
– Rotor current
– Rotor angle or the load angle

CAPABILITY DIAGRAM OF GENERATOR
 Capability diagram of Generators give the safe operating
regimes and limitations etc. This is of great help to the
operating Engineers to ensure operations of the machines
accordingly.
 Their information particularly for limiting zones of operations
are useful in setting the various limiters of Automatic Voltage
Regulator.
 100 MW Turbo-Generator of 0.80 p.f. (nominal) rating and
having a SCR of 0.60
 MW values are marked on Y axis and MVAR values on X-axis
on per unit basis of rated MVA

 Safety factor a 12.5 percent (or 1.125 p.u) power margin to
increase in power demand with no corresponding increase in
excitation “Practical Stability Limit Line”.
• (125 x 0.6)=75 MVAR i.e. 0.6 pu
• From the point „A‟ the dotted line „AS‟ denotes the theoretical
stability line.
• Horizontal lines parallel to X-axis denote the MW (constant power)
lines.

 Power intervals P equal to the required safety margin, in this
case 0.125 p.u. of rated power i.e., (0.8 x 0.125) = 0.10 p.u. of
MVA at points e,d,c,b and a.
 With radii Aa, Ab, Ac, Ad and Ae arcs of circles are drawn
with A as centre to cut the 0.8, 0.6, 0.4, 0.2 and zero power
lines.
• These intercepts are then joined by a continuous curve F B
G. - “Practical Stability Line” for a 12.5% power margin.

 The reasoning behind this construction
 take the case of „Aa‟ arc. This point 1 (or B) would be working point
of the machine at 0.8 p.u. MVA power with an excitation of „Aa‟
Amps.
• Since the basis of the safety margin is that there should be
provision for increase in power without any change in excitation,
the working point 1 would move along arc of radius (fixed
excitation) towards theoretical pull-out line .
• It is just sufficient to support 0.9 MVA i.e., 1.125 p.u. power
(presuming turbine has the capability)

 Next, with “0” as centre draw a line OE at an angle of Cos-1 0.80
(36o ) (rated p.f. angle) to the Y-axis to cut the rated MW line
(Turbine limit line) at E. Rated MVA is denoted by radius OE.
 The line AE represents the CMR excitation required. With A as
centre and AE as radius, draw an arc of a circle ED representing
excitation (or Rotor heating) limit.
 The diagram FBED is the „Capability Diagram” of the machine.

Usefulness of capability Diagram for
Excitation Control System
• The information given by the capability diagram regarding full load
rotor current (excitation) maximum rotor angle during steady state
leading p.f. zone operation etc., are essential for proper setting of
the various limiters in the excitation control system.
 In power system operation, the importance and necessity of fast
acting and reliable excitation control system is well known.
• Capability diagram gives the basic information regarding the
limiting Zones of Operation so that limiters can be
set/commissioned suitably for safe operation of the units.

Rotor current limiter
• The AVR drive the field or the thyristor network into overload for one
or more of the following reasons :
• a) faulty handling
• b) system voltage reduction
• c) loss of sensing voltage to AVR and
• d) failure within the controller.

Rotor current limiter
• The excitation limiter must prevent this overload from persisting.
• On the other hand, during dynamic disturbances in the system the
excitation should not be reduced at once, but ceiling excitation
should be possible for a limited time.

ROTOR CURRENT LIMITER

• The field current is measured on the a.c. input side of the
thyristor converter
• It is converted into proportional d.c. voltages.
• The signal is compared with an adjustable reference value,
amplified, and with necessary time lapse fed to the voltage
regulator input.

• Rotor current limiter avoids thermal overloading of the rotor
winding and is provided to protect the generator rotor against
excessively long duration over loads.
• The ceiling excitation is limited to a predetermined limit and is
allowed to flow for a time which is dependant upon the rate of rise
of field current before being limited to the thermal limit value.

Stator current limiter
• The stator current limiter has to influence the AVR differently
depending on whether the machine is over-excited or under-
excited.
• The excitation current is to be suitably reduced to limit the
inductive stator current
• The excitation current is increased to limit the capacitive current.

• Capacitive stator current limitation comes into play only with
synchronous condensers which are to some extent negatively
excited with generators
• It prevents excessive leading MVAR loading corresponding to any
given MW load.

STATOR CURRENT LIMITER

• The generator stator current is converted into polarised dc signal +ve
or –ve, depending upon whether the machine is over-excited or under-
excited.
• This voltage forms the actual value for the controllers which process
each of the bipolar signal independently.
• One of the these controllers compare the capacitive stator current
against its reference and acts directly on the regulator via a de-coupling
diode to increase the excitation.

• The action of second controller which limits the inductive stator current
is delayed by means of an integrator before it influences the control
input of the AVR so as to reduce the excitation.
• The time lag offered is perfectly acceptable as far as stator overheating
is concerned.
• The integrator time constant is set one order less than the stator
thermal time constant.

Rotor Angle Limiter
• The rotor angle limiter limits the load angle of the machine to an
acceptable present value.
• The load angle is the electrical angle between the voltage vector of the
system and the vector of the machine voltage ‘e’
• The rotor angle limiter provides a more definite protection in
preventing the machine from falling out of step.

Rotor Angle Limiter
• In the event of a short circuit in the systems, the generators may
accelerate owing to the abrupt partial removal of the electrical load.
• As the turbine governor cannot act fast, the rotor angle increases and
the angle can become so large relative to the system vector that the
machine may fall out of step.

ROTOR ANGLE LIMITER

Slip Stabilizing Units
• The slip stabilizing unit is used for the suppression of rotor
oscillations of the alternator through the additional
influence of excitation.
• The slip as well as acceleration signals needed for the
stabilization are derived from active power delivered by the
alternator.
• Both the signals, which are correspondingly amplified and
summed up, influence the excitation of the synchronous
machine through AVR in a manner as to suppress the Rotor
oscillations.

DIGITAL AVR / SEE
• AN IDEAL CHOICE FOR POWER STATIONS OPTING FOR
• RETROFIT OF EXCITATION CONTROL EQUIPMENT
AND
• FOR NEW POWER STATIONS EMPLOYING DCS
SYSTEMS

PF CompensationVectorial Addition
If f < fo
f
Frequency Circuit
Max
Error Detector
Set Value
PID Controller
Pulse Generator
Pulse range
5 - 30  , 120- 170
D/A
Thyristor cubical
Firing Pulse
Controller
Sensing Circuit
CT
Stator current from ‘T’ phase
A/D
PT
Stator voltage from ‘R’ and ‘S’ phase
A/D
Current – Voltage Transformer
yes
no
G
3Phase supply

FEATURES AVAILABLE
• FOUR OPERATING MODES :
• VOLTAGE REGULATION,
• FIELD CURRENT REGULATION,
• PF REGULATION AND
• VAR REGULATION
• SMOOTH CHANGEOVER AMONG THE CHANNELS
• UNDER EXCITATION LIMITING
• OVER EXCITATION LIMITING
• AUTO OVER-FLUXING PREVENTION (V/F LIMITER)
FOLLOW-UP TO MATCH ACTIVE & NON-ACTIVE CHANNEL
OUTPUTS FOR SMOOTH CHANGEOVER

FEATURES AVAILABLE
• SET-POINT ADJUSTMENTS FOR AUTO AND MANUAL CHANNELS
• GENERATOR OVER-VOLTAGE & UNDER-VOLTAGE
PROTECTIONS
• COMPOUNDING FOR PARALLEL OPERATION OF GENERATORS
• FIELD OVER-VOLTAGE & OVER-CURRENT PROTECTIONS
• DETECTION OF LOSS OF SENSING
• SOFT START VOLTAGE BUILD-UP
• DATA COMMUNICATION TO DCS SYSTEM ON MODBUS
PROTOCOL
• LOCAL MENU DRIVEN HMI (HUMAN MACHINE INTERFACE) & PC
CONTROLLED PARAMETER ADJUSTMENT
• TRANSIENT RESPONSE RECORDING
• n-1 REDUNDANCY IN THYRISTOR BRIDGES
• REDUNDANCY IN CONTROLLER (OPTIONAL)

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