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Ze & Ipscc

Frankie 223
I am preparing an electrical model for a project and have asked ukpn to confirm the Ze, Ipscc and Z% of the transformer so I can input the data in the software.


I got the following figures back which I am not sure I understand:

Ze=0.15

Ipscc=32kA

Z for the 11kV/400V 1.5MVA Tx 5.5%


Based on the Tx Z and Ipscc I would expect a much lower Ze. Am I missing something or do you think that the above figures make sense?
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    Sounds to me like UKPN have just quoted their usual worst-case values - which allows them an amount of leeway for future network changes. 0.15 Ohms sounds like 300A or more supply.


    It's the same if you asked about a domestic single-phase PME supply you'd usually get the answer 16kA and 0.35 Ohms, which clearly doesn't stack up since the L-N and L-PE loop are identical (L-PEN) - what they're really saying is that the loop impedance could be anything between about 0.014 Ohms (16kA) (worst case for breaking capacity) and 0.35 Ohms (about 0.6kA) (worst case for ADS) and ideally your design could cope with anything between the two because you might wake up one morning to find the the DNO have changed things.


       - Andy.
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  • 0
    Sounds to me like UKPN have just quoted their usual worst-case values - which allows them an amount of leeway for future network changes. 0.15 Ohms sounds like 300A or more supply.


    It's the same if you asked about a domestic single-phase PME supply you'd usually get the answer 16kA and 0.35 Ohms, which clearly doesn't stack up since the L-N and L-PE loop are identical (L-PEN) - what they're really saying is that the loop impedance could be anything between about 0.014 Ohms (16kA) (worst case for breaking capacity) and 0.35 Ohms (about 0.6kA) (worst case for ADS) and ideally your design could cope with anything between the two because you might wake up one morning to find the the DNO have changed things.


       - Andy.
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