Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 1 HV and EHV allocation of harmonic rights

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 2 Present condition ER G5/4 stage 3 assessment: applies to connection of loads at and above 33kV. final stage that should be followed for connections between low voltage and 33kV when leads to a not acceptable outcome under stage 2 assessment. Current practice under G5/4 Stage 3 assessment is to allow maximum planning levels to be taken up by developers on a “first come and first served” basis.

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 3 Comparison of IEC and ER G5/4 IECG5/4 Stage 1 (simple assessment): Simple procedure for connections of small loads. Based on load and short circuit level – Equal rights Doesn’t specify a simple connection assessment similar to stage 1 of IEC. Only stage 3 is defined for HV and EHV. Stage 2 (detail assessment): Identifies a global maximum harmonic level for the substation of interest considering substations in the neighbourhood. The global limit is allocated based on customer load and total capacity of the substation- Equal rights. Stage 3 requires a detail assessment for identifying the limits. However, all the available limits are given to the first customer. Stage 3 (exceptional cases): acceptance of higher levels on a conditional and precarious basis Also has suggestions how to deal with cases where harmonic levels may exceed planning levels.

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 4 Pros and Cons IECG5/4 Stage 1 Pro. Simple connection assessment made based on the rating of connect load Con. Doesn’t give the possibility to account for the effects of existing background harmonic conditions Stage 3 of G5/4 Pro. Possibility to account for the effects of existing background harmonic conditions. Con. Requires every customer to go through a detailed harmonic assessment irrespective of size of the load if connected above 33kV Stage 2 Pro. The method always tends to leave an inherent margin in the system. Con. the remaining proportion of the global limit may never be used up and first customer could incur unnecessary investment. Pro. Early bird catches the worm- the first customer gets all the available head room. Con. Customers wanting to connect to the same substation at a later stage will have extremely tight limits or no head room at all

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 5 Global harmonic level

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 6 Best of both? In order to balance between network performance and customer investments on harmonic mitigation, provisions could be made in the G5/4 to take advantage of both approaches. In substations where multiple connections are envisaged (possibly up to 7 years) the limits could be based on equal rights i.e., IEC apportioning method. In substations where multiple connections are not envisaged the present G5/4 approach of first come first served practice could be maintained. These two approaches rely on the number of planning applications made to the utility.

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 7 Scenario – if multiple connection requests have been made C1 C2 C3 C1 – applies for connection C2 – applies for connection C3 – applies for connection It may also be that a single customer may have applied for more than one connection. C1, C2 and C2 could be allocated based on IEC equal rights.

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 8 C1 Scenario – if only a single connection is made or envisaged C1 could be allocated all available margin.

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 9 Issues Will the information available be sufficient to make a fair judgement on number of connections likely to happen in a given substation? Should the substation capacity be calculated for the time of connection? Customer may complain about all available head rooms not being provided.

Energy SectorEnergy Automation: Shafiu © Siemens AG 2010 Page 10 Background harmonic amplification Simulation results done on windfarms have shown background harmonic amplification as high as 6 times. ….generally, the longer the cable the higher the amplification of the background harmonics.