Busbar Presentation Draft

NUMERICAL BUSBAR BREAKER FALURE PROTECTION

WITH REB 500

HIMANSHU SEKHAR GHADEI

ENGINEER/MRT

TIRUNELVELI

Busbar protection is provided for high speed sensitive clearance of busbar faults by tripping all the circuit breakers connected to faulty bus

BUSBAR PROTECTION GENERAL

In absence of fault clearance takes place in Zone-II(300ms) of distance protection in remote end and reverse zone 5(1.5 sec) bydistance protection own end.

NEED OF BUSBAR PROTECTION

REQUIREMENT OF BUSBAR PROTECTION•Short tripping time

•Detect internal fault

•Stable at external fault

•Isolation of faulty bus

•Secure against mal-operation of auxiliary contact.

SILENT FEATURES

Low-impedance busbar protection

Fast clearance of busbar faults.

Reliable fault isolation.

Avoid heavy damage of primary and secondary equipments.

Less copper wiring (Replaced by fiber)

Continuous self supervision enhances reliability and availability.

Functionality mainly defined by software.

Disturbance recorder/analysis.

Synchronous Event logger.

Less maintenance.

Future extension is possible

STATION AUTOMATION SYSTEM (SAS)

The REB500 system can be integrated in a station automation system (SAS) with IEC 61850

DISTRIBUTED INSTALLATION

The bay units are installed in the control and protection cubicles associated with the individual switchgear bays and the central unit is located on its own normally in a relay equipment room.

CENTRAL UNIT AND BAY UNIT

The structure of the protection system is bay-oriented. The bay units are located close to the switchgear in control bay kiosks . Distributed bay units are connected to the central unit by an optical fibre process bus. The central unit collects all the data and executes the protection algorithms and auxiliary functions at station level.

AI

BI/BO

AI

BI/BO

BAY UNITS AT TIRUNELVELI

400 kV Main 1= 31 nos400 kV Main II=18nos 220 kV =10nos

CENTRAL UNITS AT TIRUNELVELI

400 kV -2 nos

220 kV=1 nos

401

402

403

404

405

406

407

409

410

411

412

413

415

416

417

418

419

421

422

423

424

425

426

427

408 414 420

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1 M1 M1 M1 M1 M1 M1 M1 M1

M1 M1

BR-1 UDPT -1 UDPT 1 LR

KKM -2

UDPT -2 UDPT 2 LR

MDU -1 TVM -1MDU -2 TVM -2

ICT-1 ICT-2 ICT-F KKM- 3 BR-2 CHN-1 CHN-2KKM- 1 LINE-F

CIRCUIT BREAKER

400 KV MAIN I BU

400 KV MAIN II BU

BUS-1

BUS-2

BUSBAR STRUCTURE AT TIRUNELVELI

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1 M1 M1 M1 M1 M1 M1 M1 M1

M1 M1

BR-1UDPT -1

UDPT 1 LR

KKM -2UDPT -2

UDPT 2 LR

MDU -2 MDU -1 TVM -1 TVM -2


BUS BAR CENTRAL

UNIT-1

KIOSK-9 KIOSK-8 KIOSK-7 KIOSK-6 KIOSK-5 KIOSK-2 KIOSK-1KIOSK-4 KIOSK-3

BUS BAR CENTRAL

UNIT-2

400 KV BUSBAR STRUCTURE IN TIRUNELVELI

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1 M1 M1 M1 M1 M1 M1 M1 M1

M1 M1

BR-1UDPT -1

UDPT 1 LR

KKM -2UDPT -2

UDPT 2 LR



BUS BAR CENTRAL

UNIT-1

KIOSK-9 KIOSK-8 KIOSK-7 KIOSK-6 KIOSK-5 KIOSK-4 KIOSK-3 KIOSK-2 KIOSK-1

SAS

400 KV BUSBAR MAIN I OPTICAL NETWORK

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1

M2

M1 M1 M1 M1 M1 M1 M1 M1 M1

M1 M1

BR-1UDPT -1

UDPT 1 LR

KKM -2UDPT -2

UDPT 2 LR



KIOSK-9 KIOSK-8 KIOSK-7 KIOSK-6 KIOSK-5 KIOSK-4 KIOSK-3 KIOSK-2 KIOSK-1

BUS BAR CENTRAL

UNIT-2

SAS

400 KV BUSBAR MAIN II OPTICAL NETWORK

TBC BC ICT F ICT II ICT I LINE-I LINE-II LINE-3 LINE-4 LINE-5

BUS-1

BUS-2

TBC

BU BU BU BU BU BU BU BU BU BU

KIOSK 1 KIOSK 2 KIOSK 3 KIOSK 4 KIOSK 5

CU

220 KV BUSBAR STRUCTURE AND OPTICAL NETWORK

400 KV BUSBAR MAIN I

BUSBAR IMAGE

The busbar image is based on a topological principleTopological items are:

BusbarsIsolatorsCircuit breakersCTsFeeders

SIGNAL ACQUISITION AND PROCESSING

REB500 processes the current measurements digitally in the bay units

Sampling rate for 50 Hz is 2.4 kHz and for 60 Hz it is 2.88 kHz.

In case of CT saturation , the signals are compensated by the digital signal processor (DSP) according to the maximum prolongation principle.

The signals then pass through a Fourier filter, which separates the real and imaginary fundamental frequency components.

All the other harmonics are suppressed.

These components are evaluated by all the protection functions in the bay units.

The current signals are also transferred to the central unit, which executes the busbar protection function.

MAXIMUM PROLONGATION PRINCIPLE

The maximum prolongation principle is a method for processing the current signals to enable the protection algorithms to detect faults discriminatively even if CTs are saturating.

MAXIMUM PROLONGATION PRINCIPLE

Time t0 is the interval between the last zero crossing before the maximum value is detected and the end of the prolongation period.

The rise time from the zero crossing to the maximum value is defined as ta. The difference between to and ta is time th, which is then the time the maximum value in the sampling window is prolonged.

The longer time ta, the shorter the maximum value is prolonged.

BUSBAR PROTECTION

The protection algorithms are based on twowell-proven measuring principles

A stabilized differential current measurement.

The determination of the phase relationship between the feeder currents (phase comparison).

DIFFERENTIAL CURRENT MEASUREMENT

The algorithms process complex current vectors which are obtained by Fourier analysis and only contain the fundamental frequency component. Any DC component and harmonics are suppressed.The first measuring principle uses a stabilized differential current algorithm. The currents are evaluated individually for each of the phases and each section of busbar (protection zone)

Differential Current=

Restraint Current=

where N is the number of feeders.The following two conditions have to be accomplished for the detection of an internal faultThe above calculations and evaluations are performed by the central unit.

stabilizing factor=

IK min =differential current pick-up value

TYPICAL EXAMPLE FOR BUSBAR PROTECTION

A) CT circuit fault on bay 1ΔI = IB2 + IB3 = 2 kA. False tripping can be avoided by setting :IKmin > 2 kA

B) CT circuit fault on bay 2ΔI = IB1 - IB3 = 1.7 kA

False tripping can thus be avoided by:IKmin > 1.7 kA and k > 0.74

C) CT circuit fault on bay 3ΔI = IB1 - IB2 = 0.3 kA

False tripping can thus be avoided by:IKmin > 1.7 kA and k > 0.74

The best solution in this situation is to set IKmin to 80% of theminimum fault current.

PHASE COMPARISON

This principle determines the direction of energy flow and involves comparing the phases of the currents of all the feeders connected to a busbar section.

The fundamental frequency current phasorsare compared. In the case of an internal fault, all of the feeder currents have almost the same phase angle, while in normaloperation or during an external fault at leastone current is approximately 180° out ofphase with the others.

DIFFICULTY OF CONVENTIONAL HIGH IMPEDANCE DIFFERENTIAL PROTECTION

Current transformer saturation.

Knee point requirement

Current transformer ratio mismatch

BREAKER FAILURE PROTECTION

•According to CIGRE breaker fails to operate once in every10,000 attempts for normal load current & fault current.

•According to NGC there is a failure to operate per 1,000 attempts to interrupt fault current.

CAUSES OF BREAKER FALURE

BREAKER FAILURE PROTECTION

The breaker failure functions in the bay unitsmonitor the phase currents independently ofthe busbar protection. They have two timerswith individual settings.

Operation of the breaker failure function Externally via a binary input, e.g. by the line protection, transformer protection etc.

FAULT INCIDENCE

Tripping command by protection

Successful tripping by main protection

Yes

No

Start breaker failure timer

Tripping command BFP T1

Successful back up trip T1

NoInter trip command BFP

T2

Yes

BREAKER FAILURE FLOW DIAGRAM

BREAKER FALURE PROTECTION CASE-1



BUS BAR STABILITY

Stability test conducted as pre-commissioning test before charging new feeder.

Busbar protection differential current measured during testing for stable (normal)/ unstable condition.

Instable condition is created by swapping the current transformer secondary core. Feeders

Busbar

BZ-1

BZ-2

BUS-1

BUS-2

BUS BAR STABILITY

CURRENT PATH

Single phase or three phase Current set to flow in a closed loop through the busbar.

Normal time the bus zone differential current will be zero.

Unstable condition made by swapping CT secondary at the bay unit.

Suppose 25A current set to flow through bus-1 R- PhaseThen Normal time

BZ1 differential current:

L1=0,L2=0,L3=0

Stabilizing Factor=0/50=0

After changing the CT secondary the differential current will be

L1=50,L2=0,L3=0

And stabilizing factor will be =50/50=1

Thank You

Documents

Busbar Presentation Draft