Protection Relays

Electrical and electronical CAD Electronical
1

Hello

 

In a HVA type electrical network, what is the difference between a direct protection relay and an indirect protection relay?

 

Thanks in advance

2
Uh, without any particular knowledge, I would say that a direct protection relay works on the voltage of the network while an indirect one works in another quantity (temperature,..) but good to take with a lot of caution given my limited skills.
3

Hello

 

The difference between the two is as follows:

  • Direct contact:

It is the contact with the electrical parts of the equipment, contactors, etc. Basically, putting your finger directly on contactors is direct contact.

  • Contact Indirect:

It is the fact of being indirectly affected by the current because of an insulation defect. Basically, a bare film touches the metal frame of the machine, the operator touches the casing with his fingers, he then receives indirect contact.

 

 

The main protective measures against direct contact are:

  • Insulation of the active parts of the electrical equipment (duct, etc.).
  • Protection by means of boxes, paintings, etc. which make electrical equipment inaccessible.
  • Out of reach, by distance for the HV.

 

Protection against indirect contact:

  • In the event of an insulation fault, the power supply to the circuit with the fault must be automatically switched off. The DDR (Residual Current Differential Circuit Breaker) is used. The principle is to detect the fault current that passes through the earth.
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4

In addition to what "the seagull" said (which is a good answer), I give you a link to an ERDF document on the protection of HVA networks.

http://www.erdfdistribution.fr/medias/DTR_Racc_Prod/ERDF-NOI-RES_13E.pdf