Alstom METI Directional Relays 1

[stevesummers]

Hi All,

i have come across some Alstom METI relays installed in conjunction with the Alstom MCGG relays to give a directional control.

The METI's are set at PhA = +30deg, PhB =-45deg and PhC =+30deg. PhB being set as an earth fault.

My question is does this mean the PhA and PhC elements are set 'Reverse' and the PhB (the earth setting) is set 'Forward'..... or they are all set in the same direction, and the earth setting is negative angle because the earth fault current lags instead of leads (or is it the other way around i can never remember)?

I assume it is the latter case, and the earth value is set minus because of the sequence currents...

I know i should be able to work it out in theory, but i'm in a bit of a rush

Ta
Steve

 

[marks1080]

I can't directly help you with your question... but i did find an old manual (correction 'brochure') that I think will help you.

See attached....

 

[Hoxton]

Oh, happy days.

you need to google "St Leonards Works Stafford"

Eventually you will find your way to getting a copy of the manual, not the brochure you were given.

I used to work for GEC Measurements Stafford, and sold many MCCG and METI

As I say to many, 'I spent my career shutting down British industry’

Arnold Weinstock must be spinning in his grave!

 

[DiscoP]

St Leonards works is now closed - but they are still in the Stafford area trading as GE Grid.

The settings look pretty normal - however it all depends on the voltages that are connected.

E/F is normally a comparison between -V0 and +I0, hence the -ve angle.

For the phase elements, normally IA is compared to Vb-Vc and IC to Va-Vb, hence the +ve angle.

If it is connected like this, then all elements are looking the same way.

The best guide to use is the NPAG (formerly called PRAG). You used to be able to download it as a PDF from their website

 

[RRaghunath]

DiscoP has answered your question already. Just to add to his post,
if the power system is resistance earthed, the characteristic angle setting recommended is 0degrees.
That's because in case of earth faults with resistor in neutral-to-earth circuit, the fault current (Io) will be in phase with the residual voltage (Vo).

Rompicherla Raghunath