innovative use of auxiliary bus in an ehv switch-yard - a

7TH. CONFERENCE ON ADVANCES AND

INNOVATIONS IN SUB STATIONS AT CBIP HALL,

NEW DELHI, ON THE 25TH -26TH JULY 2019

Innovative use of Auxiliary Bus in an EHV

Switch-yard - A case history narrating extension of 220

kV supply to needy 220 kV S/S at Sarni in MPPTCL.

By K.K.Murty, Retd. C.E. (T&C),MPPTCL and M.Y.Mansoori E.E.(Testing)

Sagar, MPPTCL.

SYNOPSIS

Bus -systems play a vital role in a GRID network.

The Bus configurations in 220 kV system & above are generally ; 2 Main bus + an Auxiliary bus system.

1&1/2 Breaker scheme.

Main Focus: Uninterrupted power–supply to the load/consumers.

Breaker maintenance/Testing & Breaker replacement without interruption.

Authors had extended supply to 220kV needy S/s with an innovative use of 220 kV Aux.bus in an EHV Switch-yard.

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K K Murty & MY Mansoori

AUXILIARY BUS CONFIGURATION

It is strung with the same sized conductors as the main bus.

It has connection to the main bus 1&2 through main bus 1&2 main bus isolators (as the case may be) ,a circuit breaker ,CTs and aux bus isolator.

Each bay is equipped with auxiliary bus isolator.

CTs are placed/erected at ”T” point.

The figure in the next slide depicts the concept of an Auxiliary bus and how it is utilised in by-passing the bay Circuit breaker for maintenance/ replacement without interruption.

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KKMurty & MY Mansoori

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A MAIN BUS & AN AUX BUS SYSTEM

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K K Murty & MY Mansoori 4

EXTENDING 220KV SUPPLY TO NEEDY

220KV S/S SARNI THROUGH INNOVATIVE

IDEA USING AUX BUS;

Case history:

Incidence

Express/ mail and goods train stopped plying with electric

locomotives between the Itarsi Rly Jn. to Nagpur Rly Jn.

(Grand-Trunk route) and vice versa.

Reason ;

non-availability of traction supply from 132/25kV Traction

s/s.

As the source 220 kV Substation at Sarni (MP) was

deprived of 220 kV Supply.

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GRID NETWORK AROUND SSTPS & SUPPLY

TO 220KV S/S. SARNI

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FEED TO RLY TRACTION S/S BETWEEN

ITARSI JN TO NAGPUR JN

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AFFECT DUE TO THE INCIDENCE

Non -Tripping of breaker of 220kV Sarni S/s feeder on fault has affected the system as well as to Rlys as under;

(1)

Since 220kV Sarni S/s is very near, all the GSUs(Gen.Step up Transformers )and all the feeders on that particular bus tripped(the fault was as severe as Bus fault) .

Cascade tripping took place in the GRID causing System disturbance.

Deficit of power experienced in the GRID.

(2)

Interruption of supply to all 132/25kV Traction Sub stations between Itarsi Rly Jn and Nagpur Rly Jn.causing all the en-route trains to halt wherever they were i between Itarsi Rly Jn to Nagpur Rly Jn and vice versa( Grand Trunk route).

The System was normalized immediately by ousting the 220kV SSTPS-220kV Sarni S/S feeder.

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RCA OF FAULT & NON-TRIPPING OF BREAKER

It was a man-made Ph to Ground fault created by a shepherd by throwing a metallic Chain /wire on to this 220 kV Transmission Line -touching the transmission line tower very near to SSTPS bus..

DPR operated on Ph to E/F protection in Zone 1 and had sent the trip command to the Breaker.

SF6 breaker(WH make)did not trip(open) due to some mechanical problem.

Note: LBB protection was not in operation at that time .

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STEPS/ MEASURES TAKEN BY THE RAILWAYS

TO COMBAT THE SITUATION:

The Railways had to switch-over to use diesel locos

for pulling the important Mail, Express & Goods

Trains plying between Itarsi Jn to Nagpur Jn and vice

versa.(Trunk Route)

Frantic FAX messages sent to the Chairman, MPSEB,

requesting resumption of supply to their 132/25 KV

Traction Substations immediately

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CHALLENGE: HOW TO EXTEND 20KV SUPPLY TO

220KV SARNI S/S IN MINIMAL POSSIBLE TIME?

EHT Const/Maint Engineers were proposing to erect a structure out side SSTPS Switch Yard and tie the 220kV Sarni feeder with the neighbouring 220kV feeder.

An innovative idea struck to the mind of the principal author since;

i. the old 220kV corridor (through 220kV Itarsi-4nos feeders) for evacuation of Power of 300 MW STPS has almost become redundant,,

ii. use Aux. Bus available in the 220kV Switch-yard of SSTPS as tie link to connect 220kV Sarni S/S feeder with one of the 4 Nos. -220kV feeders from SSTPS to 220kV S/S Itarsi

iii. thus convert this feeder as 220kV Itarsi-220kV Sarni S/S feeder with revising the DPR settings accordingly at Itarsi end.”

And make the saying in English language” NECESSITY IS THE MOTHER OF INVENTION” come true.

(Pl refer next slide)

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NOTE:-

Before Introduction of 400kV System in the WREB grid 220kV

feeders namely 220kV STPS – Itarsi feeders-4 Nos. were the

only corridor for power evacuation from 300 MW STPS.

With the introduction of 400kV system and with enhanced the

installed capacity of 1130 MW, turning this Thermal Power

Station as Super Thermal Power Station, the 4 Nos - 220kV

feeders from SSTPS to Itarsi had lost their importance.

To transmit load from SSTPS to 220kV S/S Itarsi was adequate

to be catered with 3- no. 220kV SSTPA-220kV Itarsi feeders.

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IMPLEMENTATION OF INNOVATIVE IDEA

Operations in the switchyard; 1) tying SSTPS-Itarsi fdr.3 with 220 Sarni s/s feeder by

closing the Aux Bus Isolator of 220kV SSTPS -220kV Sarni S/s and the Aux.bus isolator of 220kV SSTPS-220kV Itarsi fdr-3.

2) keeping Main bus isolators and Line side Isolators and the circuit breakers of 220kV Itarsi feeder no3 and 220kV Sarni S/s feeder open,

3) Revising DPR settings at Itarsi end.

With execution of these operations the 220kV supply could be extended to the 220kV S/s Sarni ,

Subequently132kV feeders could be energised and supply to 132/25 kV Rly Traction S/s could be resumed.

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EXTENSION OF 220 KV SUPPLY

TO SARNI S/S

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CONCLUSIONS:

Advantages;

By implementing this innovative method, following advantages could be achieved;

Curbing dissatisfaction of the Indian Railway Authorities towards MPPTCL.

Saving on time,

Saving on investment on arranging erection of structure for tying any 220kV feeder with 220kV Sarni S/S feeder outside the Switch yard.

Saving on manpower.

This system is foolproof and can last for any length of time without any system constraints.

Caution: This episode is an eye opener episode/incidence calling for attention to keep the LBB protection (Now known as 50BFP) always in healthy condition in all the EHV sub stations/Switch yards of the Power Stations.

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PRINCIPAL AUTHOR’S ACKNOWLEDGEMENTS,

I express my gratitude to MD, MPPTCL for permitting me to make

Er. M.Y.Mansoori as my co-Author and to use data of 220kV Sarni S/s.

I express my gratitude to the CBIP for giving me this opportunity to present this paper.

I extend my gratitude to the distinguished guests and expert professionals present in this hall for patiently listening to my presentation and deliberation.

I dedicate this paper to my beloved wife Late Mrs.K.Vijaya Murty, who had been always a source of inspiration and encouragement to me.

Er.K.K.Murty.BE( Hons),FIE ,CE(Ind)

Member CIGRE’India

Mob:+91 9425154250

e-mail Id:[email protected]

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innovative use of auxiliary bus in an ehv switch-yard - a

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