Ripple signal amplification: measurement, modelling and mitigation

Use of high frequency ripple control signals for load control purposes has existed for many years. Although the level of the injected signal at the zone substation is generally small, amplification can occur when the network resonant frequency is close to the injected ripple signal frequency. Ripple signal level at the injection point is generally 5 – 7V in magnitude with reference to public low voltage systems. However, in some cases, network resonance can lead to voltage levels in excess of 10V that can lead to equipment problems the most prevalent being ‘racing clocks’. This phenomenon is essentially waveform distortion causing extra zero crossings. The paper presents the findings of a monitoring campaign and network modelling and simulation study carried out on a network owned and operated by Integral Energy. The potential mitigation strategies that could be used to alleviate ripple signal amplification are also discussed.