HVI vs Load Break vs Isolation Device

[ChrisCentral]

Hi All - I am reading through some documents that Hydro One in Ontario has published; after some quick googling I can't seem to find the difference between:
High Voltage Interrupting Device
High Voltage Isolation Device
High Voltage Load Break Switch

Can someone please give me a quick difference between each of the above??

Thanks!!

 

[big john]

Can't guarantee they're using the same terminology, but as I'm familiar with it:

An "interrupter" is any device capable of opening the circuit, however it may not be rated for opening while under load. A gang-operated air-break switch is an example of a non-load rated interrupter. Where an SF6 breaker would be an example of a load rated interrupter.

An "isolation device" is anything used to establish a line clearance for safety purposes. Many places require a visible air-break in the line, and this is what the isolation device accomplishes. It can be an air-switch that is opened, load-break elbows that are pulled, or a breaker that is racked out, etc. The isolation device is a type of interrupter, however, if they specifically require visible air-breaks then not all interrupters would qualify as "isolation devices."

A "load break switch" is also a type of interrupter, but it is specifically rated to open the circuit under loaded operating conditions. This could be a style of disconnect switch or circuit breaker. But again, since not all interrupters are rated for load break, that's why this specific designation exists.

 

[Jraef]

Can't guarantee they're using the same terminology, but as I'm familiar with it:

An "interrupter" is any device capable of opening the circuit, however it may not be rated for opening while under load. A gang-operated air-break switch is an example of a non-load rated interrupter. Where an SF6 breaker would be an example of a load rated interrupter.

An "isolation device" is anything used to establish a line clearance for safety purposes. Many places require a visible air-break in the line, and this is what the isolation device accomplishes. It can be an air-switch that is opened, load-break elbows that are pulled, or a breaker that is racked out, etc. The isolation device is a type of interrupter, however, if they specifically require visible air-breaks then not all interrupters would qualify as "isolation devices."

A "load break switch" is also a type of interrupter, but it is specifically rated to open the circuit under loaded operating conditions. This could be a style of disconnect switch or circuit breaker. But again, since not all interrupters are rated for load break, that's why this specific designation exists.

That's a good explanation.

I'll only add an example: an isolation switch is typically used IN CONJUNCTION with another switching device and actually turns the power off. For example, vacuum contactors are not actually as safe as some people believe, because if they open under fault conditions there is a possibility of vaporized contact material inside of the vacuum bottle coating the inside of the bottle. Because the separation gap in a vacuum bottle is so small, there is a high possibility of leakage, which at MV levels, would be lethal. So an isolation switch is opened AFTER the vacuum contactor does its job.