hi guys
i have a practical question
i wanted to know if a same earth well connection is used for DC filters and converters in converter station????
or the use seprated ground connections?(one earth well and earth connection for DC filters and another for converters)
There are different types of earth electrode connections besides well type. There are separate earth connections with many earth switches in between and all separate earth connections converge into one main electrode connection. Off-course the connection of separate earthing depend upon specific topology. I would recommend you reading this document for more details.
http://www.cigre.cl/wp-content/uploads/2017/02/Brochure-Cigre-FRancia-HVDC-Electrones-675.pdf
2. http://cigre.ru/research_commitets/ik_rus/b4_rus/library/ALSTOM_HVDC_for_Beginners_and_Beyond.pdf
3. http://www.skb.com/publication/2485831/R-14-34.pdf
I agree with Asma, There are different types of earth electrode connections with are separate earth connections and many earth switche.
converter earthing needs a perfect ground which is difficult to get close to station .Normally an electrode line is run 10 to sometimes 50 km to get an ideal earth, A huge area with buried conductors connected by copper pipes with coke and sart is built to which the elctrode line is connected at several points. The elecrode line is insulated typically with 11 or 22 kV insulators and electrode line arresters are located at converter end, Because of exposed electrode line it can be subjected to lightning surges.
Neutral bus switches, Neutral bus ground switches Metallic return transfer switches are provided to switch over from ground return mode to metallic return mode and vice versa.
DC filters can have their local ground or the points connected to neutral bus ultimately going to earthing pit.
The arresters in DC filter ckt in such cases need coordination with the neutral bus arresters.
The one answer to the question is that all possible ways of grounding is possible depending on property of earth, some are technically and economically superior.
The problem is one of insulation coordination and , allowable spill DC in neighbouring AC system neutals. corrosion issues .
From the electromagnetic compatibility point of view, and under normal grounding resistances, it is better to separate the ground connections of the filters, and the converters. You may refer to the IEC standard.
I fully agree, More so for high capacity HVDC projects with long lines. Tripathy
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