HR and LRM systems

[snehalatha]

Hello everyone,
I am currently trying to understand HR and LRM systems in swiitchgears which is used for voltage detection. Can someone explain what is LRM and HR system?

Any help is appreciated.

Thank you

 

[Paul.M]

Welcome to the forum.

 

[snehalatha]

Welcome to the forum.

Thank you

 

[obebokek]

is there any update?

 

[seltechpc]

HR and LRM stands for High Resistance and Low Resistance-Modified. It is a system used in metal clad switchgear to monitor and measure voltage via a capacitive network for isolation. In some HV and EHV applications they are known as CVT's or Capacitor Voltage Transformers. These are clearly a fixed part of the installation

 

[obebokek]

Thanks for your reply. Could you please specify a bit more how/when we use LRM and HR system? Input impedance of LRM is around 2M ohm, HR:36M ohm. But what is the advantages/disatvangates of using HR or LRM systems?

 

[seltechpc]

As I understand it the two systems effectively are different physically so you can only plug the appropriate one in the correct socket. This also applies to the verification or proving units.
The important thing to remember is this is used for Safe Isolation and verification so usual rules apply regarding using the proving units. I assume the different impedances are for different voltages.

It sounds as though this may be a college/exam question. I left college 50 years ago before these devices were invented, although there were more bulky equivalents. I suggest an email to Siemens Switchgear division and ask their technical teams what are the engineering considerations for the two.