We specialize in refurbishing M.V. switchgear to the clients specification. The panels
are stripped completely then sandblasted and powder coated to suit your requirements.
We can disassemble and reassemble most makes and models of circuit breakers and ring
main units. We also do repairs and maintenance on most circuit breakers. Our wiring
team is capable of wiring protection schemes, control panels, circuit breakers and
mini sub L.V. cubicles.
We are capable of installing and commissioning of most makes & models of switchgear
(indoor or outdoor).
We also specialize in the installation and maintenance of GIS switchgear especially
the Alstom WS.
Retrofit, Replacement or Refurbishment of Switchgear
1) When faced with ageing switchgear that no longer meet your requirements, you are
normally faced with these three options : retrofit, replacement or refurbishment
of that switchgear.
2) The problems you may encounter are summarized below:
a) SAFETY
Modern switchgear have evolved to a point where it is safer to operate than the old
switchgear. The modern trend towards safety and user liability makes this an important
criteria.
b) OPERABILITY
Networks are becoming more and more automated. This may require technology far beyond
the capability of the old switchgear.
c) MAINTAINABILTY
Availability of skilled personnel may become a problem and prices might be exorbitant.
d) AVAILIBILTY OF SPARES
Parts have a limited production life as technology improvements cause them to be
superseded. Lack of spares normally result in malfunctions or equipment being beyond
repair.
3) Once you have decided you are faced with 3 options:
a) REPLACEMENT
The old switchgear is stripped out and completely replaced with new switchgear.
b) REFURBISHMENT
Here you retain the old switchgear and do an extensive overhaul. Critical parts may
be replaced. The main feature is that the old switchgear is not modified.
c) RETROFITTING
Retrofitting is the replacement of certain parts of the switchgear. This could be
only the circuit breaker, protection & control or certain current carrying parts,
but keeping the basic structure or enclosure.
4) Advantages and Disadvantages. These are listed in the tables on the right below.
5) Testing
With retrofits or refurbishment there arises some questions like – can the switchgear
conform to certain specification such as , short circuit , BIL, ability to break
faults etc.
There are four possibilities to overcome this problem - type test, extrapolation,
calculation, approximation and synthesis
a) Type test
Here one manufactures a prototype and performs the relevant tests. There are limitations
such as cost, time constraints, failure and rework and difficulty in obtaining the
prototype.
It is only viable if you are retrofitting large quantities so that you can spread
the cost.
b) Approximation & Extrapolation
If you have existing data on the circuit breaker that verifies its performance, you
could extrapolate that data to the new installation if its important features are
not changed eg.
Busbar sizes, contact arrangements and clearance.
One could then state with a degree of certainty that the retrofits performance would
be met.
c) Synthesis
If each building block has to be tested individually and then when brought together,
the final result could deemed acceptable by virtue of its components.
The uncertainty would be the interfacing, but this may be treated by extrapolation
or calculation.
For example if the circuit breaker and the panel had been tested individually then
you could say with a degree of certainty that the combination would meet the require
performance.
d) Calculation
It could be possible to calculate whether equipment in a retrofit would be able to
meet required performance.
