PCS 978s x datasheet EN overseas general x r1 20

 Add reactor protection application scenario  Update of technical data  Add reactor current differential protection function 87R and inter-turn fault protection function 21IT  Ad

About This Document

About This Document

The manual describes the control, protection, measurement and supervision functions with the information of relevant hardware for PCS-978S Transformer Relay

Copyright © 2020 NR All rights reserved

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Document Revision History

Document Revision History

 Update of switchgear control function

 Modification of voltage selection diagram

 Update of technical data

 Add reactor protection application scenario

 Update of technical data

 Add reactor current differential protection function 87R and

inter-turn fault protection function 21IT

 Add binary input and binary output module NR6661

 Add mechanical relay input and output module NR6662

 Replace the NET-DSP module NR6112B with NR6113

 Deletion of the DC analogue input module NR6631B

Overview

Overview

PCS-978S transformer relay has been designed specifically for the protection of various type power transformers, including two-winding transformers, three-winding transformers (up to 6 branches), auto-transformers, as well as shunt reactors PCS-978S is the main protection for the transformer and contains many other protections, control and monitoring functions With its modular structure, flexibility and the powerful PCS-Studio engineering tool, PCS-978S offers future-oriented system solutions with high investment security and low operating costs

The PCS-978S is applicable not only to conventional substations, but also to digital substations It supports IEC 61850 Editions 1 and 2 and provides GOOSE and SV network interfaces with high real-time performance The process level network supports peer-to-peer (P2P) mode and networking mode, including single network mode and dual network mode The station level network could also receive and send MMS messages (such as interlocking signals) or process level GOOSE messages (such as trip signals)

 Various function modules can satisfy various situations according to the different requirements of users Flexible and universal logic programming, user-defined configuration of BI/BOs, buttons and LEDs and powerful analog programming are supported

 Modularized hardware design makes the device be easily upgraded or repaired by a qualified service person It can be mixed with different I/O modules, with online self-check and monitoring function, and the device can be restored from abnormal operation only need to replace a single abnormal module

 Support memory check and error correction function, ensure high reliability and safety

 Support the internet communication protocol of native PRP/HSR and RSTP

 Fully compatible with IEC 61850 edition 1 & edition 2, support MMS service, IEC 62351 communication service, GOOSE communication in station level & process level, SV communication with multi-sampling rate

 Full comply with cyber security standards, including IEC62443, IEC62351, IEEE1686, NERC-CIP, support role based access control (RBAC), security audit, security encryption communication and security tool, improve the cyber security capability of devices

 Powerful COMTRADE fault and disturbance recording function is supported The whole recording time is automatically configurable by the fault duration, which is convenient to fault analysis and replay The recording sample rate is up to 9.6kHz

 Settable secondary rated current (1A/5A) and settable voltage threshold of binary input

Highlights

 PCS-Studio engineering tool is the application software on the user's PC for the interface with PCS S series devices providing all the related functionality It ranges from device configuration to full substation design of bay integration

 Support IEEE1588, IRIG-B clock synchronization

 Support actual system phase sequence, either ABC or ACB, incorrect connection of actual phase sequence can automatically be verified and relevant protection functions can be blocked

 Equipped with high-speed large capacity output relay, its operation speed is less than 1ms and its break capacity is up to 10A The real-time supervision for output drive circuit can detect the abnormality in advance

 Support setup up to 40 users and allow each user to own different password and access authority

Features

Features

 High degree of functional integration and flexible configuration modes, transformer main protection and back-up protection can be integrated in one device, or be separated in two devices

 Up to 36 analog inputs can be provided and configured flexibly

 The tripping output contacts can be configured by tripping matrix, which is flexible, convenient and suitable to any mode of tripping

 The relay supports at most 6 branches differential protection The transformer angle can be adjusted flexibly, and any transformer angle compensation mode is supported and any side can be chosen as the reference side of differential protection

 Reliable differential CT circuit failure supervision The relay can detect multi-phase CT wire-break, multi-side CT wire-break, short-circuit, and other complex situation The corresponding logic setting can be used to select blocking differential protection or not, in case of CT circuit failure

 Multiple inrush current blocking options are provided Self-adaptive inrush current blocking criterion can ensure the relay fast operation for transformer energized on to a slight fault, meanwhile it will avoid the unwanted operation in the case of the energization inrush current caused by energizing transformer with no load, the recovery inrush current caused by cutting off the transformer external fault, and the sympathetic inrush current

 Biased DPFC differential protection is regardless of load current and is sensitive to small internal fault current within the transformer Its anti CT saturation performance is also strong

51P Alm 87W 87T

Figure 1 Typical application of an auto-transformer

52 52

Figure 2 Typical application of a shunt reactor

Functions Overview

Protection Functions

87T Transformer differential protection

 Biased differential protection with three slopes

 Biased DPFC differential protection

 Unrestrained instantaneous differential protection

 Optional inrush current distinguished principles: harmonic criterion or waveform distortion

 Optional harmonic blocking modes: self-adaptive 1Pblk1P mode, 2PBlk3P mode, 1Pblk3P mode

 Overexcitation detection: fifth harmonic or third harmonic criterion

 Optional transfer methods: △→Y or Y→△

 Independent CT saturation criterion

 Differential CT circuit failure supervision

64REF Restricted earth-fault protection

 Optional direction element

 CT transient characteristic difference detection

 CT saturation detection based on 2nd and 3rd harmonics

87W Winding differential protection  CT transient characteristic difference detection

 CT saturation detection based on 2nd and 3rd harmonics

87R Reactor differential protection

 Biased DPFC differential protection

 Biased current differential protection

 Independent CT saturation criterion

 Harmonic blocking criterion

 Differential CT circuit failure supervision

21IT Inter-turn fault protection

 Zero-sequence power directional element and zero-sequence impedance element

 CT and VT circuit failure blocking

24 Overexcitation protection

 Two stages definite-time overexcitation protection

 Stage 1 of definite-time overexcitation protection for trip purpose

 Stage 2 of definite-time overexcitation protection for alarm purpose

Functions Overview

67G

50/51G

Earth fault protection

 4 stages with independent logic by default

 Optional direction element for each stage,

 Optional measured zero-sequence current or calculated zero-sequence current

 Optional definite-time characteristic and inverse-time characteristic for each stage

 Selectable trip purpose or alarm purpose for each stage

 Harmonic control element for each stage

67Q

50/51Q

Negative-sequence overcurrent

protection

 Up to 2 stages with independent logic

 Optional direction element for each stage

 Optional definite-time characteristic and inverse-time characteristic for each stage

49 Thermal overload protection  Two stages thermal overload protection, and one stage for

alarm purpose and the other stage for trip purpose

50BF Breaker failure protection

 Up to 6 circuit breakers are supported

 Phase-segregated re-trip and three-phases re-trip

 Optional current criterion (phase overcurrent element, zero-sequence overcurrent element, negative-sequence overcurrent element)

 Optional circuit breaker position check

 Two time delays

59P Overvoltage protection

 Up to 2 stages with independent logic

 Optional definite-time characteristic and inverse-time characteristic for each stage

 Optional phase voltage or phase-to-phase voltage

 Optional “1-out-of-3” logic or “3-out-of-3” logic

 Selectable trip purpose or alarm purpose for each stage

27P Undervoltage protection

 Up to 2 stages with independent logic

 Optional definite-time characteristic and inverse-time characteristic for each stage

 Optional phase voltage or phase-to-phase voltage

 Optional “1-out-of-3” logic or “3-out-of-3” logic

 Blocked by instantaneous VT circuit failure

 Selectable trip purpose or alarm purpose for each stage

59G Residual overvoltage protection

 Up to 2 stages with independent logic

 Optional measured zero-sequence voltage or calculated zero-sequence voltage

 Optional definite-time characteristic and inverse-time characteristic for each stage

 Selectable trip purpose or alarm purpose for each stage

81O Overfrequency protection  Up to 2 stages with independent logic

 Voltage control element

Functions Overview

81U Underfrequency protection  Up to 4 stages with independent logic

 Voltage control element

Control Functions

 Switchgear control

 Double point status synthesis

 Remote/Local control mode switch

 Interlocking logic for control

 Direct control

 Closing synchronism check with voltage selection

 Switchgear trip counter

 Tap position indicator and control

Measurement and Metering Functions

 CT circuit failure Supervision (CTS)

 VT circuit failure Supervision (VTS)

 Self diagnostic

 Powerful faults recording (max buffer for 10,000 sampled points at 4.8 or 9.6 kHz)

 Event Recorder including 1024 disturbance records, 1024 binary events, 1024 supervision events,

Functions Overview

Modbus, DNP3.0, IEC 60870-5-103, IEC 61850 Ed.1 & Ed.2, IEC 61850 MMS Server, IEC 61850-8-1 GOOSE, IEC 61850-9-2LE SV, IEC 62439 Parallel Redundancy Protocol, IEC 62439 HSR Ring Redundancy Protocol

 Up to four 10Base-T/100Base-TX copper Ethernet ports

 Up to fourteen 100Base-FX optical Ethernet ports

 Up to four 1000Base-SX optical Ethernet ports

 Two RS-485 serial ports for communication or printer

 One RS-485/TTL serial port for clock synchronization

 Two RJ45 debugging ports (front and rear)

 4 Programmable operator pushbuttons with user-configurable labels

 Up to 18 programmable target LEDs with user-configurable labels

 1 RS-485 rear ports for printer

 Language switchover—English+ selected language

 Configuration tool—PCS-Studio

Additional Functions

 User programmable logic

 Switching system phase sequences function (ABC or ACB)

 Clock synchronization

 IRIG-B: IRIG-B via RS-485 differential level, TTL level or optical fibre interface

 PPS: Pulse per second (PPS) via RS-485 differential level or binary input

 PPM: Pulse per minute (PPM) via RS-485 differential level or binary input

 IEEE 1588: Clock message based on IEEE 1588 via optical fibre interface

 SNTP (PTP): Unicast (point-to-point) SNTP mode via Ethernet network

 SNTP (BC): Broadcast SNTP mode via Ethernet network

Typical Application

Typical Application

PCS-978S can be applied for a two-winding transformer, three-winding transformer or auto-transformer

in any voltage level, or a shunt reactor PCS-978S provides full transformer protections which are configurable by user Ancillary functions of fault diagnostic, disturbance records, event records and communication function are integrated in the device

PCS-978S is adaptive to the following 2/3-windings transformers or autotransformer

Protection Functions

Protection Functions

Transformer Current Differential Protection (87T)

In power system, the power transformer is one of most valuable and expensive equipment If a fault occurs in the protection zone of a transformer, current differential protection operates quickly to clear the fault to avoid the transformer from damages or reduce the maintenance cost as low as possible

Transformer differential protection supports up to 6 group CT inputs, and can be used for 2-windings, 3-windings transformer and auto-transformer There are 24 vector groups available for two-winding transformer and 288 vector groups available for 3-winding transformer

Transformer differential protection includes biased differential element, instantaneous differential element, DPFC biased differential element Biased differential element is biased characteristic with three slopes Instantaneous differential element is without biased characteristic and blocking logic and can accelerate to operate for transformer's severe internal faults DPFC biased differential element calculated by current variation has high sensitivity to inter-turn faults and high-impedance fault under heavy load Three differential elements mentioned above work coordinately to form the high-speed current differential protection with high sensitivity

Restricted Earth Fault Protection (64REF)

Restricted earth fault protection (REF) is meant to protect a single winding of a power transformer, and the protected winding must be earthed In the case of delta windings, the winding must be earthed by an earthing transformer, which must be electrically placed between the winding and the current transformers REF can be applied to protection of two-winding transformer, three-winding transformer or auto-transformer

REF is a kind of differential protection, so it calculates differential current and restrained current The differential current is a vector difference of the neutral current (i.e., current flowing in the neutral conductor) and the residual current from the lines For internal faults, this difference is equal to the total earth fault current REF operates on the fault current only, and is not dependent on eventual load currents This makes REF a very sensitive protection

The difference between current differential protection and REF is that the first one is based on adjusted phase current balance and the latter is based on balance of calculated residual current and residual current from neutral CT

Three groups of REF are for each side of a three-winding transformer at most REF is not affected by inrush current and the tap of transformer CT Transient detection function based on the ratio of residual current to positive current is adopted to eliminate the influence of difference of transient characteristic to REF

compensation 3I0Cal'_H2

Magnitude compensation

Figure 8 Application for two-winding transformer with two CBs at one side

REF at HV side

Magnitude compensation

Figure 9 Application for auto-transformer

Maximum 4 group of CTs and 1 neutral point CT inputs for REF, and the maximum current inputs applied for an auto-transformer with two circuit breakers at HV and MV sides respectively

Winding Differential Protection (87W)

When each side and common winding of auto-transformer are installed with three phase CTs, winding differential protection can be equipped Winding differential protection is based on Kirchhoff's law, so inrush current has no effect on it Winding differential protection consists of phase winding differential protection and residual winding differential protection Residual winding differential protection adopts the calculated residual current of each side and common winding for the protection calculation and three-phase CT polarity is easy to be checked The operation principle of which is similar to that of REF, but compared to REF, winding differential protection can operate not only during internal earth faults but also during phase-to-phase faults

Winding differential protection is based on Kirchhoff's first law and calculates differential currents of electrical connection circuits including phase A, phase B phase C and residual differential currents Inrush current and tap change of the transformer have no effect on winding differential protection Winding differential protection has high sensitivity to internal earth faults because there is no load current

in the restraint current Normally, winding differential protection is applied in following two situations

REF at HV side

Magnitude compensation

Figure 10 Winding differential protection applied to auto-transformer

Magnitude

protection Magnitude

to accelerate the operating speed for reactor's severe internal faults without biased characteristic and blocking elements DPFC biased differential element calculated by current variation has high sensitivity

to earth faults at ground end of reactor Zero-sequence differential element based on calculated residual current of two sides of reactor has high sensitivity to asymmetric fault Above four differential protection elements work coordinately to form the high-speed current differential protection with high sensitivity

Inter-turn Fault Protection (21IT)

Shunt reactors as the key equipment are widely applied in extra-high voltage and ultra-high voltage level power system, which has a dominate effect on safe operation of the power system The inter-turn fault is

a common internal fault occurred in reactor, but current differential protection cannot operate during inter-turn faults Considering earth fault protection cannot be taken as the fast protection for inter-turn faults, a dedicated protection for inter-turn protection of reactor is needed to be equipped

Inter-turn faults in reactors present a formidable challenge to the protection engineer The current and voltage changes encountered during an inter-turn fault can be of similar magnitude as load variation, and therefore, sensitive, reliable protection schemes should be considered

Inter-turn fault protection consists of zero-sequence power direction element and zero-sequence impedance element They can improve sensitivity and ensure the device against maloperation during external faults, transient process (such as series compensated lines, LC resonance, power swing etc.)

or abnormal conditions (such as pole disagreement, CT secondary circuit failure, etc.)

Inter-turn fault protection adopts the current from CT at line side of reactor The amplitude of residual voltage is compensated to ensure zero-sequence power direction element can distinguish direction correctly when system impedance is too low Inter-turn fault protection will be blocked during CT and VT circuit failure

Overexcitation Protection (24)

Overexcitation results from excessive applied voltage, possibly in combination with below-normal frequency Such condition may occur when a unit is on load, but are more likely to arise when it is on open circuit, or at a loss of load occurrence Transformers directly connected to generators are in particular danger to experience overexcitation condition

During overexcitation, field current of transformer rises greatly to cause excessive heating and severe damage The transformer, working magnetic flux density near the knee point, is subject to overexcitation Frequency range for normal operation is 45~55Hz for 50Hz working frequency of power system and 55~65Hz for 60Hz working frequency of power system

Overexcitation protection can be configured at any side of transformer through PCS-Studio, and it is

Protection Functions

recommended to be equipped at the side without OLTC

Overexcitation protection consists of two stages definite-time overexcitation protection and one stage inverse-time overexcitation protection for trip purpose or alarm purpose The voltage for protection calculation is RMS of three phase voltages and not affected by frequency fluctuation Overexcitation inverse-time curve is sectional linear curve, which has high adaptability

Phase Overcurrent Protection (50/51P, 67P)

The device can provide 6 stages of phase overcurrent protection with independent logic Each stage can

be independently set as definite-time characteristics or inverse-time characteristics The dropout characteristics can be set as instantaneous dropout, definite-time dropout or inverse-time dropout Users can choose whether it is blocked by the voltage control element, direction control element, or harmonic control element The direction control element can be set as no direction, forward direction and reverse direction The phase overcurrent protection picks up when the current exceeds the current threshold value, and operates after a certain time delay, once the fault disappears, the phase overcurrent protection will dropout

Earth Fault Overcurrent Protection (50/51G, 67G)

The device can provide 4 stages of earth fault overcurrent protection with independent logic Each stage can be independently set as definite-time characteristics or inverse-time characteristics The dropout characteristics can be set as immediate dropout, definite-time dropout or inverse-time dropout Users can choose whether it is blocked by the direction control element or the harmonic control element The direction control element can be set as no direction, forward direction and reverse direction The zero-sequence current used by earth fault overcurrent protection can be calculated zero-sequence current or the measured zero-sequence current, it can operate to trip or alarm, it can be enabled or blocked by the external binary input

Negative-sequence Overcurrent Protection (50/51Q, 67Q)

The device can provide two stages of negative-sequence overcurrent protection with independent logic Each stage can be independently set as definite-time characteristics or inverse-time characteristics The dropout characteristics can be set as immediate dropout, definite-time dropout or inverse-time dropout For a double-circuit or a ring network line, the negative-sequence fault current may have different flow direction Considering the protection selectivity, the negative-sequence overcurrent protection can be blocked by the direction control element Negative-sequence overcurrent current can operate to trip or

Protection Functions

estimation is made based on the measured currents and the built thermal model of the transformer with two time constants

Breaker Failure Protection (50BF)

According to the tripping information from the device and the auxiliary information (the current and the position) of target circuit breaker, breaker failure protection constitutes the criterion to discriminate whether the target circuit fails to open If the criterion is confirmed, breaker failure protection will operate

to trip the target circuit breaker with the re-tripping time delay, trip it again with the first time delay and trip the adjacent circuit breakers with the second time delay As a special backup protection, breaker failure protection can quickly isolate the fault, reduce the affected range by the fault, keep system stability and prevent generators, transformers and other primary equipments from seriously damaged For breaker failure protection, phase-segregated re-trip, three-phases re-trip and two time delays are available

Phase Overvoltage Protection (59P)

The device can provide two stages of phase overvoltage protection with independent logic When a high voltage occurs in the system, it is greater than the voltage threshold, phase overvoltage protection will operate to remove the device from the system after a time delay In addition, the overvoltage protection also provides the alarm function, prompting the overvoltage of the system, it allows users to find the cause timely, and preventing further deterioration of the fault Each stage of phase overvoltage protection can be independently set as definite-time characteristics or inverse-time characteristics The dropout characteristics can be set as immediate dropout and definite-time dropout

Users can select phase voltage or phase-to-phase voltage for the protection calculation

“1-out-of-3” or “3-out-of-3” logic can be selected for the protection criterion (1-out-of-3 means any of three phase voltages, 3-out-of-3 means all three phase voltages)

Phase Undervoltage Protection (27P)

The device can provide two stages of phase undervoltage protection with independent logic When the voltage drops in the system and it is lower than the voltage threshold, phase undervoltage protection will operate

Taking into account that the role of undervoltage protection is to remove the running device from the system, but in order to prevent undervoltage protection is always operating when it is not charged, the breaker closed position check criterion is added, users can choose to detect the breaker position, current

or no-check as the releasing condition for the protection

In addition, the undervoltage protection also provides the alarm function, prompting the undervoltage of the system, it allows users to find the cause timely, and preventing further deterioration of the fault Each stage of phase undervoltage protection can be independently set as definite-time characteristics or inverse-time characteristics The dropout characteristics can be set as immediate dropout and definite-time dropout

Users can select phase voltage or phase-to-phase voltage for the protection calculation

Protection Functions

“1-out-of-3” or “3-out-of-3” logic can be selected for the protection criterion (1-out-of-3 means any of three phase voltages, 3-out-of-3 means all three phase voltages)

Residual Overvoltage Protection (59G)

The device can provide two stages of residual overvoltage protection with independent logic When the residual voltage is greater than the voltage threshold, the residual overvoltage protection will operate to remove the device from the system after a time delay In addition, the residual overvoltage protection also provides the alarm function, it prompt that there is an earth fault leading to residual voltage generation, it allows users to find the cause timely, and preventing further deterioration of the fault The dropout characteristics of residual overvoltage protection can be set as immediate dropout and definite-time dropout

Overfrequency Protection (81O)

The device can provide two stages of overfrequency protection If the system frequency is greater than the setting, overfrequency protection will operate to remove some part of active power supplies from the system Overfrequency protection is with independent definite-time characteristics and with instantaneous dropout characteristics

Underfrequency Protection (81U)

The device can provide four stages of underfrequency protection If the system frequency is less than the setting, underfrequency protection will operate to shedding some part of loads from the system Underfrequency protection is with independent definite-time characteristics and with instantaneous dropout characteristics

a local control The switchgear control function is closely related to interlocking, double point status (DPS), remote/local control mode switching and trip counter

A control command can realize various control signals such as the CB/DS/ES opening/closing In order

to ensure the reliability of the control output, a locking circuit is added to each control object The operation is strictly in accordance with the selection, check and execution steps, to ensure that the control operation can be safely and reliably implemented In addition, the device has a hardware self-checking and blocking function to prevent hardware damage from maloperation output

The switchgear control function can cooperate with functions such as synchronism check and interlocking criteria calculation to complete the output of the corresponding operation command It can realize the normal control output in one bay and the interlocking and programmable logic configuration between bays

This device supports the following functional control module:

CSWI Control of circuit breaker (CB), disconnector switch (DS) or earthing switch (ES)

RMTLOC Remote or local control mode

XCBR Synthesis of CB position, three-phase or phase separated

XSWI Synthesis of DS/ES position

SXCBR/SCSWI Trip counter of CB/DS/ES

RSYN Synchronism check for CB closing

CILO Interlocking logic for CB/DS/ES control

MCSWI Manual control of CB/DS/ES

CHKPOS Position verification for switchgear control

Remote/Local Control Mode Switch

Since the source of a control command may be SAS or NCC, or may be triggered by the device LCD or terminal contact, it is necessary to provide a remote/local control mode switch function

The remote/local control mode switch function determines whether the device is in the remote or the local control permission state through the configuration of terminal contact, function key, or binary signal Each control object provides a remote/local input, and the control module determines the current control authority to be remote or local according to the input value By default, if the input is not configured, any control operation is blocked

Control Functions

Double Point Status

A double point status (DPS), which usually indicates switchgear status, can be derived from 2 ordinary binary inputs The unit also supports the DPS synthesis through switchgear opening and closing positions after jittering processing The synthetic DPS contains original SOE timestamp The CB control function supports phase-separated position inputs and can synthesize these inputs into general position

Trip Counter

The trip counter function takes the DPS of switchgear position as input count the trip times For CB, this device supports phase-segregated and general trip counter The trip counter function is triggered by DPS change The counting result is stored in non-volatile memory for power-off holding

Interlocking

The interlocking function will influence the control operation output When the function is enabled, the device determines whether the control operation is permitted based on the interlocking logic result Each control object is equipped with an independent interlocking logic which supports unlocking operation through a binary signal

The interlocking function is very important for the control operation of switchgears During the operation

of primary equipment, the positions of the relevant equipment must be correct for operation permission For remote control, i.e command from SAS or NCC, this device could judge the interlocking logic depending on the message within the command; for local control through device LCD or terminal contact, please use the corresponding logic setting to enable/disable the interlocking function

Control Functions

Voltage Selection

The voltage selection function can be used to switch the reference and synchronization v oltages for the synchronism check function in double busbars and one-and-half circuit breakers scenarios, or to switch three-phase voltages among double busbars used by protection calculations or measurements The

"Near priority" principle is adopted by default, and the user interface for programmable switching logic is also reserved

The voltage selection module is used in the following scenarios:

 For single circuit breaker with double busbars, the selection of appropriate voltage from both busbars for synchronism check is required Line VT input is taken as reference

Ua Ub Uc

Bus2 Bus1

DS1.DPS

DS2.DPS

UB1 UB2

Control Functions

 For single circuit breaker with double busbars, the selection of three-phase voltage from both busbars is used as reference voltage of synchronism check Single-phase voltage from line VT is the synchronization voltage

Ua Ub Uc

Bus2 Bus1

DS1.DPS

DS2.DPS UB2

DS1 DS2

CB

Line UL1

Ua Ub Uc UB1

Figure 13 Voltage connection for double busbars 2

Control Functions

 For one-and-half breakers arrangement in the application scenario of double circuit breakers, the selection of voltage from Line1 VT, Line2 VT and Bus 2 VT is the reference voltage to check synchronism with Bus1 voltage for the closing operation of Bus1 side circuit breaker

Ua Ub Uc UB1

UL2 UL1 

Figure 14 Voltage connection for one-and-half breakers arrangement

Tap Position Indicator

A tap changer is a connection point selection mechanism along a power transformer winding that allows

a variable number of turns to be selected in discrete steps A transformer with a variable turn's ratio is produced, enabling stepped voltage regulation of the output The tap selection may be made via an automatic or manual tap changer mechanism

The Tap Position Indicator (TPI) input could be 6-bit Binary-Coded Decimal (BCD), independent contacts, carry inputs or DC analog input The indicator supports phase-separated inputs and discordance alarm