Utilities Middle East – August 2019

KNOWLEDGE PARTNER

30 Utilities Middle East / August 2019 http://www.utilities-me.com

E

very protection system must work

safely, quickly and in a targeted

manner. The aim of this requirement

is to deliver a supply of energy that is

as stable as possible and, most importantly,

to ensure the safety of electrical energy facil-

ities.

In the fi eld of relay testing, various suppli-

ers off ering well-proven devices together

with a generally accepted set of methods

regarding how testing is to be carried out

have been around for many years. However,

even the most thoroughly tested protection

relay will not be doing its job if it is unable to

detect an event caused by a one-off wiring

error.

Wiring testing is, therefore, vital - especially

when commissioning a new or modifi ed

installation - and should be a process carried

but not all of them are examined in detail.

If we look at the confi guration that crops

up most frequently in the fi eld, that is, a

three-phase system with three current and

three voltage transformers, the following

errors might occur. They should, therefore,

be looked for every time a test is carried out;

incorrect polarity in the current transformer,

current transformer installed in wrong

direction, current transformer circuit not

grounded, additional unintentional ground

connections and malfunction of a relay test

plug or relay test connector.

Other elements to be looked for include

break in the secondary wiring of current or

voltage transformers, polarity error in the

secondary wiring, phase reversal in the sec-

ondary wiring and installation direction of

current transformer incorrectly set in relay.

out according to a standard that is likewise

broadly accepted.

Operators of electrical energy facilities

have shown there does not appear to be an

established standard for wiring testing. Most

companies rely on an in-house process for

wiring testing that has been developed over

the years from their respective experiences.

The basic idea behind this approach

addresses the question of what errors should

be found (or, ideally, not found) when test-

ing wiring. In this article, the authors propose

a reliable method for wiring testing that has

been developed on the basis of this question

and the fi ndings from the interviews.

It can be carried out with minimal outlay

while providing as high a level of safety as

possible. To keep the length of this article

within bounds, the various steps are listed,

With the COMPANO 100, OMICRON has developed a test set that is optimised to test the wiring

from the transformers to the relays, meters or control room

RELIABLE TESTING OF TRANSFORMER

WIRING - A POOR RELATION?