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Do you need a special kind of joint like bimetalic one?

Without mechanical diagram can you explain S1 and S2 switches only? Or at least tell me which one can be used for indication, tripping, blocking, interlocking?

On high voltage circuit breaker schematics there are circuit breaker auxiliary switches S1, S2, S3, S4. All can be normally open, normally closed, late break, early make. But what is the difference between them? The only explanation that I have found anywhere states the following: Auxiliary...

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So, the main principles of interlocking are: 1. You can't operate disconnector unless associated circuit breaker is open; 2. You can't close earth switch unless associated disconnector is open; 3. You can't Close the disconnector while the associated earth switch is closed to earth; This can...

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Gas insulated equipment containing high pressure compartments, e.g. 145kV and 72.5kV gas insulated switchgear is normally provided with “plug in” cable connectors. The normal operating practice is that no work should be carried out on gas insulated High Voltage systems on one side of a gas...

I understand what multiplexing is, i.e. transmitting several different signals via one channel. I just want some practical examples. 1. Assuming we have 96F fibre cable, which comprises 96 fibre strands. We can either connect 96 relays via this fibre cable directly. Or we can connect all of...

When doing protection grading studies for HV and EHV networks usual grading margins are 200-350ms depending on relay types (fast numerical vs slow electromechanical) and circuit breaker types (fast new vacuum vs slow old oil). When doing protection grading on LV networks I believe the rule of...

Are multicore cables clamped directly to steel support structure?

If pilot multicore cable is installed next to a power cable there will be induced voltage within the pilot cable. The magnitude of 50 Hz induced voltage depends on: (a) the distance between the power cable, or line, and the auxiliary cable; (b) the magnitude of the current in the power circuit...

Is there any good book that would explain this subject (ideally based on UK, but not essential)? I know "Keith Harker - Power System Commissioning and Maintenance Practice", its quite good but is very broad and covers everything from relay protection to cables, and primary commissioning. I would...

The board is equipped with vacuum circuit breakers. Therefore busbar chamber is sf6 insulated.

I understand that you need them to isolate tripping functions, but what would be the reason why you would want to isolate certain trip functions? Looking at attached circuit breaker DC schematic example: LK10 (light blue) BUS ZONE TRIP ISOLATION - I assume you need to remove this link if you...

Sulfur hexafluoride. Insulating gas.

If you order high voltage SF6 indoor metalclad switchboard comprising several panels does it arrive on site from the manufacturer as a whole switchboard unit or as separate panels?

In below example distance between cable cleats is 500mm. The cable is 1000mm2. What distance would you have for 630mm2 cable. Above image shows one cable sealing end structure. We have 3 in total (1 per phase). Distance between each other is 3m. I have calculated that short circuit force on...

I understand transformer vector groups, however I get confused when it comes to changing phase order outside the transformer to change it's vector group. For example the following statement: "For this connection the outer HV phase conductors are effectively swapped, with phase Red connected to...

Three structures, each housing one single core cable.

When you have a dual ratio CT, say 1000/500/1, and the thermal rating of CT is 100%. Does this mean that on the 1000/1 ratio you will 1000 A thermal rating and on the 500/1 ratio you will have 500 A thermal rating. Or is thermal rating independent of the ratio you choose and it will be 1000 A in...