Key Questions to Ask When Ordering high voltage switchgear

About temperature rise test

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Question:What is the length of the connection row for temperature rise test?

Answer:The length of the external connection row for the temperature rise test is not less than 2 meters. According to the standard, the temperature rise should be measured 1 meter away from the test terminals of the switchgear cabinet and compared with the temperature rise of the nearest point inside the switchgear cabinet, which should not be more than 5k, in order to verify that there is no significant import or export of heat into or out of the switchgear cabinet by the external connection row.

Question:How can the temperature rise test meet the customer's requirement of 60 Hz?

Answer:According to IEC-200 standard, the temperature rise test according to 50Hz, need to have 5% margin can be considered to meet the requirements of 60Hz, there is no 60Hz test power supply, there are generally two practices, one is in accordance with the rated current, the calculation of the final temperature rise value of the margin. Another practice is to test according to 1.05 times the rated current, the temperature rise value needs to meet the standard requirements. Generally speaking, the first method is easier to pass the test.

Question:How to simulate the middle cabinet test?

Answer:Temperature rise test needs to be in accordance with the intermediate cabinet test, and the general customer test is often carried out on a single prototype, this will need to simulate the intermediate cabinet, in accordance with the standard needs to be used on both sides of the test cabinet 50mm thick foam board affixed to simulate the intermediate cabinet of the heat dissipation environment. Of course, there are also using multiple switchgear directly for the test, because the test cabinet on both sides of the cabinet generally do not have through current or rated current, so multiple cabinet test is often easier to pass than a single cabinet to paste the foam board.

Question: Double or multi-layer circuit breaker circuit breaker switchgear how to carry out temperature rise test?

Answer: and the current does not exceed 630A three-level switch can be used three-pole series connection, the same way, multi-layer circuit breaker switchgear can be used to test the multi-layer circuit breakers in series, you can also be the main bus into the line, according to the rated current of each circuit breaker through the current test.

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About Dynamic Thermal Stability

Question: How to carry out dynamic thermal stability test for grounding contact of circuit breaker trolley?

Answer: Generally, the circuit breaker trolley is only used as protective grounding, according to the determination of resistance less than 0.1 ohm, there is no need to carry out dynamic thermal stability test. Special requirements such as IEEE C37.20.2 standard switchgear, the circuit breaker compartment needs to be used as the grounding contact connection of the grounding trolley G&T, then it is necessary to carry out the dynamic thermal stability test, and can be used together with the grounding trolley test to verify the grounding contact.

Question:How to verify the dynamic thermal stability of the switchgear main bus?

Answer:Since the dynamic thermal stability test is normally performed using one switchgear cabinet, the main busbar needs to be supported separately as an incoming line to avoid damage to the switchgear cabinet caused by peak withstand external connections. Unless more than one switchgear is used for the test, there is no dynamic thermal stability test verification of the main busbar for the general type test.

Question:Do I have to do the dynamic and thermal stability tests of the main circuit and the grounding switch together?

Answer:They can be done together or separately. Doing them separately ensures that the tests are passed one by one, while doing them together fails both the main circuit and the earthing switch.

Question:Can dynamic stability and thermal stability be done separately?

Answer:Can they be done separately, i.e., according to the standard, the short-time withstand current (thermal stability) and peak withstand current (dynamic stability) test values are tested separately to determine whether they pass or not.

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kingpb said: I would get a hold of the Cutler Hammer Consulting Application Guide, and start reading the upfront sections, and look through the various equipment sections. There is a lot of information, that will help get you oriented. Then you can start asking more specific questions.

Kingpb has an excellent idea. For someone new in the industry, the manufacturer's product books are an excellent way to start becoming familar with products. Most if not all product books can be had for free, just by going to different websites and requesting them.

Good luck and stick with this industry... it is the best!!!

templdl said: As I understand it electrical equipment that contained breakers that could be withdrawn form their enclosure by means of a rack and pinion type gear mechanism was said to be switchgear.
It is common for both low and medium voltage enclosed breaker enclosure lineups to allow the removal and installation of breakers in a similar fashion to be refered to as switchgear.
Today the term switchgear appears to include any electrical equipment that is made up of floor standing enclosures.

No.
Within the moniker "switchgear", there is Metal-Clad draw-out switchgear, which is what you just described, and there is also Metal Enclosed Interrupter Switchgear (MEIS), which is NOT draw-out.

Switchgear = Individual switching devices in a lineup, sometimes can include only 1 device in the "lineup", sometimes there are versions with special "2-high" units. Can be circuit breakers, vacuum breakers, fused switches, even motor controllers. The operative issue is no matter what the design, each switch unit is fully isolated from any other one by metal barriers, so if a fault happens in one circuit, the damage does not spread to other units.

Switchboard = a group of switches all in the same cabinet, no isolation in between devices. Usually involves fused switches as opposed to circuit breakers. Less expensive than Switchgear, but runs the risk that a fault in one device will take down the entire system. Some people opt for this because everything in the system is interdependent anyway, but this is being used less and less, especially with the new Arc-Flash safety requirements. I see the day when switchboards will be no more.

Panelboard = a grouping of molded case or insulated case circuit breakers. Same as a switchboard concept but because each breaker is in its own case, fault management is easier. Usually refers to Low Voltage (600V and under) only.

Load Center = el-cheap-o version of a panelboard typically foound in residential applications where cost is king. Fault management by virtue of containment of the flames to within the box, but newer cheaper "home-line" versions are coming out with plastic boxes, so even that may be going by the wayside..