Latvia´s new energostandard "medium voltage network neutral regimes"

Latvia´s Electrotechnical Committee (LEK) recently approved new standard LEK136 “Use of neutral regimes in medium voltage networks” which is in force since September 1st 2013. LEK 136 is a unique standard among other standardization organizations like European Standards (EN) and International Electrotechnical Committee (IEC) as both do not have standards that regulate selection of medium voltage network neutral regimes. LEK136 defines criteria when isolated, compensated and resistive (low ohmic) neutral earthing system should be used in Latvian DSO AS “Sadales tikls” (ST) operated network. Latvia´s largest DSO ST maintains power supply to its customers during sustained earth fault in an isolated or compensated neutral networks. LEK standard include single phase earth fault experiment results in Latvia´s medium voltage network and original touch voltage estimation method in case of sustained earth fault in medium voltage network. Estimation method includes practical calculation for Latvia´s DSO ST and is in accordance with standard EN 50522 requirements. Electrical safety requirements for operative personnel are developed based on the estimated results.