Picture 1 – Cable ladders at Consumer’s High Voltage Switchgears
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These pictures were taken inside the Consumer HV Room of a new office building.
Picture 1 above shows the cable ladder connecting to the consumer HV switchgear panels.
Observe that there are four switchgear panels there.
On the cable ladders, there are only three HV cables. Is one of the HV switchgear panels kept as a spare?
Nope. Actually the supply authority’s HV Room is just next door to the consumer HV Room. The multi-core 11kV cable feeding supply to the consumer HV switchgears is run inside a cable trench connecting the two HV rooms. So it is not visible here.
To beginners in electrical installation works, observe carefully how the cable ladders are hung from the concrete slab using steel hanger rods. Observe also how close the spacing between adjacent hanger rods.
HV cables are heavy. The weight of the cables is one thing. There are also the bending forces of the cable when they are routed and bent along the cable ladders. At certain positions along the cable routes, the opposing bending forces of the cable ladders add to the weight of the cable itself.
What you can see in Picture 1 above are only very few cables. On many occasions in you career, you will see situations where cable ladders of the size shown in the picture sag. The forces and weight from the power cables can be that strong.
Picture 2 – Close up view of an angle iron support and the hanger rods
Observe how the angle iron support is supported at each end by a hanger rod.
Picture 3 – The cable ladder connecting HV switchgears to a transformer
Here the worker standing behind the transformer enclosure is doing the termination works of the 630 mm.sq. low voltage copper cables.
Recall that here we have four HV switchgear panels. One for the incoming cable from the supply authority switchgears in the room next door. The other three are the feeder cables for the consumers’ transformers.
In many designs, a consumer substation is designed to have separate rooms for HV switchgears and transformers. Here it has been designed to share the same room.
It does not really make much difference whether the rooms for both are shared or separate. The only real difference is the total space taken.
If separate rooms are used, it would take more space. In some installations, the space is expensive. Commercial buildings at prime areas of a big city are a classic example. Private owners count every dollar they spent on every functional space of the building. Many consider space taken by mechanical and electrical plants as a waste. So often design engineers end up with very little space to install their machines and equipment.
Here it is not so bad because it is a government office building.
The cable ladder shown in Picture 3 above provide a cable support for the HV cables from HV switchgear to a 1600 kVA transformer. This transformer serves the chiller plant behind the HV room.
The low voltage cables being terminated by the worker are also run on a cable ladder to go to the chiller plant LV switchboard.
Picture 4 – Cable ladder to 1000kVA transformers
This picture show the cable ladders to the other transformers in this substation.
Here you can see low voltage cables more clearly.
The transformers are 1000 kVA ones. While the 1600kVA transformer is dedicated to serve only the chiller plant (the main plant of the building’s centralized air-conditioning system), all other building electrical and mechanical loads including external loads (street lighting, carpark lighting, etc) are served by these two 11kV/415V transformers.
Observe how the low voltage cables coming out of the transformers are run of separate cable ladders to go to the main distribution switchboards in the LV Room at the other side of the wall.
Wall openings on the wall would later be sealed by an approved fire seal to prevent spreading of fire from one electrical room to the next.
Notice also the automatic fire suppression units (the red-painted round cylindrical objects mounted on the walls) installed at locations around the switchgear room. I will talk on the automatic fire suppression system in another post.
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