UHV and EHV circuit breaker

[climb1]

Having a debate; Is there a difference between pre-insertion resistors and closing resistors in circuit breakers?

It seems as though most manufacturers are relying more on switch sync devices instead of any mechanical resistors (pre-insertion or closing) for 345 and 500 breakers. Without influencing with my opinion, what is the preference switch synchronizing or mechanical resistor?

 

[cuky2000]

Resistors in circuit breakers can be connected with pre-insertion contacts before closing the main interrupting contacts. Breakers also could be specified with close and open resistors internally for dead-tank design or externally arranged in live-tank breakers design.

Synchronous closing is gaining acceptance slowly in the market but still pre-insertion resistors is the most effective method for controlling switching surge.

For dead-tank circuit design below 500 kV, most manufacturers can not offer insertion resistor unless using larger tank at significant extra cost. I only know one that have this option in the US and the global market.

Surge arresters have been used successfully to control switching overvoltage and in some degree to minimize the TRV tha the breaker will be exposed.

I hope this help in your discussion.

 

[odlanor]

cuky2000,
I do not agree with last paragraph. For me, surge arrester protect equipment from surge voltage originated from lightning stroke. It will be exploded if switching overvoltage exceed its caracteristics.
At EHV this could happened, so you have to dimension surge arrester to support at last one switching overvoltage that exceed the limit.
This not means to control switching overvoltage .

 

[cuky2000]

Hi Odlanor,

If your concern is the energy dissipated in the arrester during switching surge event, multiple columns arrester design are available with large energy absorption capability than the standard single column station class metal oxide surge arresters.

Surge arresters has applications beyond the traditional lightning protection at the substation entrance or close to transformer bushings.There are many application of surge arresters and varistors in series and shunt compensation, filter, HVDC and HVAC. Presently there are limited applications of circuit breaker with surge arresters as part of the interrupting circuit to increase the switching withstand capability.

After completion of the system study in one of my projects, we were able to use 345 kV dead-tank design without insertion resistors because of the surge arresters help to reduce the system switching surge from 3.4 PU to a manageable level within the rating of the circuit breaker.

Most recently, two columns surge arresters were specified in other case in TX since the energy discharge rating of the regular single column station class arresters was not rated for this application.

 

[odlanor]

cuky2000,
thanks for this update on the subject.

 

[climb1]

thank you for the information. it is most helpful.