Condition Monitoring - Td

8/8/2019 Condition Monitoring - Td

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Substation Automation SystemSubstation Automation SystemSubstation Automation SystemSubstation Automation System –––– Value Additions in Condition MonitoringValue Additions in Condition MonitoringValue Additions in Condition MonitoringValue Additions in Condition Monitoring

This paper discusses the value

additions made by automation system

in the area of condition monitoring of

CVT, imbalance bay/feeder currentswhich shows the intactness of primary

circuit and monitoring of measuring

system.

CVT ConditionCVT ConditionCVT ConditionCVT Condition MMMMonitoringonitoringonitoringonitoring

One of the best methods of

monitoring the healthiness of CVT is

by monitoring drift between phase

secondary voltages. As per

POWERGRID O&M guidelines, driftbetween CVT secondary Ph-E voltages

should not be more than 2V.

Accordingly, there was schedule of

monitoring the same quarterly. Now a

days, numerical relays/BCUs have

facility of logics to be implemented on

real time conditions. This opportunity

has been grabbed and logics

implemented at Kalivanthapattu SS

as a sample basis. The concept

considered to implement this

monitoring is as follows:

Only one core per CVT is considered

for monitoring of secondary,

preferably metering core due to higher

accuracy. Hence logics are written

onto respective BCU (metering core

always connected to BCU) that was

supplied along with SAS. The stations,

where BCUs are not available (ie.,

stations without SAS) logics can be

built in numerical relays ie., onprotection core of CVT and

annunciation may be wired to RTU

through a binary output of numerical

relay.

Logics for feeder CVTs, are

implemented in main bay BCUs and

for Bus CVTs, it is implemented in

BCUs supplied for measuring Bus

CVTs. Logics for Bus CVT become

difficult for the station without SAS.For such stations, alternatives may be

explored for the availability of spare

analog channels in any numerical

relay available in the station.

The logic implemented in the BCU has

been shown in Fig.1.

Fig.1 Logic for measuring CVT

Secondary Drift.

Equivalent threshold value of 2V can

be set in Set Upper Limit gate (This

gate is available in Siemens supplied

IEDs – equivalent gate available may

be used incase of other suppliers).

The logics were implemented at

Kalivanthapattu SS for all the CVT

metering cores and tested

successfully at HMI and Remote HMI

alarm for the set drift limits.

Unlike knowing the drift in monthly or

quarterly measurement, the drift

violation is known instantaneously at

HMI and Remote HMI. This will help in

preventing sudden failure/blasting ofCVTs and hence reducing line outage

due to such unwarranted occurrences.

This information speeds up taking

decisions for the replacement of faulty

CVTs and hence the replacement.

Abs Sub

Abs

Abs

1

2

Sub1

2

Sub1

2

Abs

Abs

Abs

Y

Y

Y

I/P

LIMIT

SET UP

Y

LIMIT

SET UP

Y

LIMIT

SET UP

Y

R-N VOLT

Y-N VOLT

B-N VOLT

I/P

I/P

Alarm to HMI

or BO of the



CurrentCurrentCurrentCurrent ImbalanceImbalanceImbalanceImbalance MonitoMonitoMonitoMonitoringringringring

Current in EHV circuit is generally

balanced one with small variation.

Imbalance in primary circuit may

happen due to the following reasons

• Mis – alignment of isolators

• Loosely connected jumpers

and terminal connectors of

primary circuit.

• Carbonization of terminal

connectors of primary circuit.

Why Current Imbalance Monitoring

When imbalance current due to the

aforementioned reasons left

unnoticed for a longer durations, it

may cause disastrous consequences

particularly, when one of the parallel

paths, is under shutdown. Further,

with this remote operation/SCADA

concepts, unlike manual recording,

analog data is being logged into soft

records automatically. Due to lesser

manual intervention, there is high

chance for unnoticing of such

incidences for longer durations. These

conditions cause the need of

monitoring current imbalance in the

bays/elements of switchyard,

particularly in remote stations.

Concept

Logic concept is same as used in CVT

secondary drift measurement.

Metering core of the CTs preferredwherever feasible due to more

accuracy. The concept at

Kalivanthapattu Substation uses,

feeder current imbalance (both 400kV

and 230kV), ICT current imbalance

(both HV & IV) and 400kV Tie bays,

230kV Bus Coupler and Transfer Bus

Coupler.

Except for 400kV tie bays, metering

core CTs are available to BCUs for all

the aforementioned cases. For Tie bay

measurement, the logic is built in LBB

relay ie., on protection core CT. And

Tie LBB relay is not connected to LAN

as there is no LAN port available on

the relay. The logic built on LBB relay

initiates its Binary output and is wired

to near IED and from IED, event is

routed to HMI.

Fig.2 Logic for measuring Current

Imbalance.

Equivalent threshold value can be set

based on the experience of the feeder

past history. Generally this value

ranges from 4% – 8% of the rated

current ie., 40 to 80A for a 1000/1A

CT.

As discussed earlier, this is most

important parameter to be monitored

especially for remote operated

stations. The event of imbalance

current for the said bays/elements

has been routed to local HMI at

Kalivanthapattu SS and remote HMI

at Sriperumbudur SS.

Measurement Monitoring SystemMeasurement Monitoring SystemMeasurement Monitoring SystemMeasurement Monitoring System - -- -

MW Balance MeasurementMW Balance MeasurementMW Balance MeasurementMW Balance Measurement

Abs Sub

Abs

Abs

1

2

Sub1

2

Sub1

2

Abs

Abs

Abs

Y

Y

Y

I/P

LIMIT

SET UP

Y

LIMIT

SET UP

Y

LIMIT

SET UP

Y

I-R PH I/P

I-Y PH I/P

I-B PH I/P

I/P

I/P

Alarm to HMI

or BO of the



For a substation MW of incoming and

outgoing feeders are balanced. MW

derived from in elements and out

elements can be verified for the

balance condition. Imbalance

condition may arise due to following

reasons.

• Unhealthy CT secondary circuit

• Unhealthy CVT secondary

circuit including Fuse failure

and non switching over CVT

circuits during Bus-shut downs.

• Faulty Measurement Units or

errors in configuration

Incidentally, there is no

supervision/monitoring system

available for such occurrences unless

it is detected by the manual

intervention or else during SEM data

uploading etc.,

Concept

The real time MW of incoming and

outgoing feeders are routed to logics

and compared for more than 3% error.

Incase difference between in and out

MWs becomes more than 3%,

corresponding event will be sent to

HMI and RHMI also. Two ways of MW

balance modes are being

implemented at Kalivanthapattu SS.

• MW balance of incoming and

outgoing feeders

• MW balance of HV and IV

circuits of ICTs

With this entire measurement system

comes under monitoring.

The logic implementation is done

using different available gates similar

to CVT drift measurement and Current

imbalance measurement. As analog

values are derived from different IEDs,

logic has to be written in station level

devices ie., at gateway/PAS. SICAM

PAS is a powerful tool that is supplied

by M/s. Siemens at Kalivanthapattu to

read all the station data from all IEDs

and switches and sending them to

HMI/RHMI/RLDC. Logics can also be

written at station level ie., at SICAM-

PAS. All analog values are available at

PAS, which can be tagged to logics

and logic output to be sent to HMI as

alarm.

Solutions for day to day problems can

be easily arrived at automated

substations. This proves cost

effectiveness of automated substation

in O&M era and thus it always adds

value to the existing system without



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Condition Monitoring - Td