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UK Substation batteries upgrade project.

broadgage

I refer here not to utility scale batteries for feeding power into the grid at times of shortage.

Thinking of the batteries installed for switchgear operation (often 110 volt) and for communications or remote control equipment (often 48/50 volt). I recall reading of a plan to upgrade these batteries to ones of much greater capacity in order to ride through much longer outages than were originally foreseen.

IIRC the plan or proposal was that the 50 volt batteries would be increased in capacity so as to give several days autonomy.

The 110 volt switchgear operating batteries were to be duplicated with each set giving 6 hours operation. In the event of any prolonged outage, one battery was to remain in use until automatically disconnected to avoid damage from deep discharge. The second battery was to be disconnected after  a short time and kept in reserve, still almost fully charged. To be put into service under remote manual control when needed.

The purpose was to assist in a black start after a multi day shutdown.

Does anyone have more details, links etc ?  Not certain why I have thinking about multi day shutdowns

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  • Most DNOs specify auxiliary batteries for longer than that for new HV substations, where they are required. WPD (NG!) are 72 hours, if I recall correctly; others vary a bit but in days not hours. It is also normal for the specification to require at least two strings of cells/monoblocs, such that one can be disconnected for testing or repair while the other maintains the critical protection function without any interruption. I've not noticed any major changes recently in terms of published policy.

    The duration is I suggest more because of likely duration planned switching and maintenance than any issues with the Grid as a whole, versus the cost and hassle of lugging a generator to every substation every time the network is reconfigured or a storm passes through. Note that sections of DNOs' 33kV networks, for example, are off far often than the consumer supply by design; It's designed to be used that way, with redundancy (e.g. rings) and switching used to divert around isolated sections. An auxilary supply fed from the substation NETx, for example, would be exposed to those outages so would need batteries sized accordingly. Though they often try to also get a 230/400V supply from the local MV ring as that should come back quickly as customers will be on it.

    I don't know anything about manually disconnecting a single string in times of shortage. I would be concerned in this arrangement of the mismatch in voltage / DoD when tying them back together again, plus by doubling the current you more than half the autonomy time. If 'twere me, in the event of a prolonged outage where you know you'll exceed the autonomy time and have time to get there at the start and end of the outage, I'd suggest locking open the switchgear and disconnecting both strings until preparing to re-energise... But then I don't work for a DNO!

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  • Most DNOs specify auxiliary batteries for longer than that for new HV substations, where they are required. WPD (NG!) are 72 hours, if I recall correctly; others vary a bit but in days not hours. It is also normal for the specification to require at least two strings of cells/monoblocs, such that one can be disconnected for testing or repair while the other maintains the critical protection function without any interruption. I've not noticed any major changes recently in terms of published policy.

    The duration is I suggest more because of likely duration planned switching and maintenance than any issues with the Grid as a whole, versus the cost and hassle of lugging a generator to every substation every time the network is reconfigured or a storm passes through. Note that sections of DNOs' 33kV networks, for example, are off far often than the consumer supply by design; It's designed to be used that way, with redundancy (e.g. rings) and switching used to divert around isolated sections. An auxilary supply fed from the substation NETx, for example, would be exposed to those outages so would need batteries sized accordingly. Though they often try to also get a 230/400V supply from the local MV ring as that should come back quickly as customers will be on it.

    I don't know anything about manually disconnecting a single string in times of shortage. I would be concerned in this arrangement of the mismatch in voltage / DoD when tying them back together again, plus by doubling the current you more than half the autonomy time. If 'twere me, in the event of a prolonged outage where you know you'll exceed the autonomy time and have time to get there at the start and end of the outage, I'd suggest locking open the switchgear and disconnecting both strings until preparing to re-energise... But then I don't work for a DNO!

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