Page 20 of 190 Report No.: 6068396.50 TRF No. G99/1-4_V1.0 G99/1 Clause Requirement - Test Result - Remark Verdict 9.4.4.1 EREC P29 is a planning standard which provides limits for voltage unbalance caused by uneven loading of three phase supply systems. Power Generating Modules should be capable of performing satisfactorily under the conditions it defines. The existing voltage unbalance on an urban Distribution Network rarely exceeds 0.5% but higher levels, in excess of 1%, may be experienced at times of high load and when outages occur at voltage levels above 11 kV. 1% may exist continuously due to unbalance of the system impedance (common on remote rural networks).
In addition, account can be taken of the neutralising effect of rotating plant, particularly at 11 kV and below. BS EN 50160 contains details of the variations and disturbances to the voltage which shall be taken into account in selecting equipment from an appropriate specification for installation on or connected to the Distribution Network. P 9.4.4.2 The level of voltage unbalance at the Point Of Common Coupling should be no greater than 1.3% for systems with a nominal voltage below 33 kV, or 1% for other systems with a nominal voltage no greater than 132 kV. Overall, voltage unbalance should not exceed 2% when assessed over any one minute period.
EREC P29, like all planning standards, is applicable at the time of connection. Info. 9.4.4.3 For Power Generating Facilities of 50 kW or less Section 7.5 of this document specifies maximum unbalance of Power Generating Modules. Where these requirements are met then no further action is required by the Generator. N/A 9.4.5 Power Factor correction equipment is sometimes used with Power Park Modules to decrease Reactive Power flows on the Distribution Network.
Where the Power Factor correction equipment is of a fixed output, stable operating conditions in the event of loss of the DNO supply are extremely unlikely to be maintained, and therefore no special protective actions are required in addition to the standard protection specified in this document. P 9.4.6 DC Injection P 9.4.6.1 The effects of, and therefore limits for, DC currents injected into the Distribution Network is an area currently under investigation. Until these investigations are concluded the limit for DC injection is less than 0.25% of the AC rating per Power Generating Module. See appended table. P 9.4.6.2 The main source of these emissions are from transformer-less Inverters.
Where necessary DC emission requirements can be satisfied by installing a transformer on the AC side of an Inverter. P 9.5 System Stability P