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Re: G5/9 @ 33kV
by Bryan Rendall at 2010-12-21 14:03:09 (Ask an Expert)

As an NERS accredited contractor for both 11 and 33 kV, we have done a lot of work on these connections for windpower, ranging from large windfarms down to single turbines.

There is a significant amount of work to do for a 33 kV connection, more than can be detailed in a posting on here. However, as you have knowledge of 33 kV import connections, we can skip over most of the issues (which are common to import and export), and cut straight to your title, which I assume is G59.

G59 protection can be implemented either at the substation, or at the turbines. We favour the turbines, executing a stop command, as opposed to tripping the 33 kV breaker, forcing the turbine into an emergency stop situation. Either can be, and have been accepted by the DNO's

G59 equipment needs to be witness tested by the DNO to their satisfaction, and this involves using a 3 phase injection test set to inject the relay with the variable voltage, frequency and rate of change of frequency.

There may well be other considerations that are different from import connections, namely P28 and G5/4, whereupon you would need to assess the impact on voltage and harmonics from your proposed generation.

As each connection tends to be site specific, then I would doubt that you will find a simple guide on the net. You could however start off by getting a copy of G59/2, G75, P28 and G5/4 from the ENA and have a good read up there for an idea of the general principles.

Otherwise, designing a 33 kV generation connection at 33 kV involves a great many man-weeks of works, and I would run out of characters here!


Bryan Rendall