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Design of 20kV Distribution network in Djibouti

Design of 20kV Distribution network in Djibouti

Design of 20kV Distribution network in Djibouti

(OP)
Hello all,

I'm planning to develop a suitable 20kV distribution network in an area of  Djibouti to feed small industrial units and ware house located in a certain area .Max .load requirement of per industrial units is around 700kVA and small units requirements starts from 50kVA .

Total load power requirement of the total area is about 5.5MVA .

Djibouti EDD have HT distribution voltage level are 20 kV and agree to give two cable for our area network to form a
ring network .

My proposal in my mind is to strategically locate pocket substation consists of ring main units ( 2F +1 T ee off ) with transformer of 20/.4kV , 1500kVA/1000kVA/500kVA in a ring circuit formed by EDD 2 Cables.I presume the 2 cables can be paralleled as it's feeding from same EDD substation .
  
.Both the EDD incoming cables are connected to  a  2F + 2 T RMU and from 2Tee off swiich with breaker protection feed the next located located 2F+1 T  RMU indiviudually and so on the connected to a 4 or 5 more RMU's located different places

I would like to have your inputs on the following .

1) What kind of protection I need to consider in each Ring in Ring out Switches or the protection on the Transformer feeder .
2) I'm prefer to give an O/C protection and E/F indication on each RMU on the T -off unit and Ring IN and Ring Out will be Switches with SF6 insulated .


regards ,

Rana .
 

RE: Design of 20kV Distribution network in Djibouti

Depending on costs.....

1. Direction protection on the Ring in Ring out feeders or some kind of cable differential protection.

2.On transformers of those size I would apply O/C and E/F protection, a Buchholtz relay and maybe a top oil temperature relay.

RE: Design of 20kV Distribution network in Djibouti

Sorry

Correction: Directional protection

Directional protection would be the easiest and cheapest to apply, but due to grading you can have a time-factor/time-delay at the source.
Feeder differential protection can be fast (no time delays) but there have to be some kind of communication-link between two relays (at different sides of a cable) and that can add to additional costs.

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