The Safe Electrical Technology RVD-E residual voltage device

A ‘good/low impedance earth’ may be compromised by many factors including corrosion, hot joints and ageing installations but the most variable and overlooked factor is the ground itself. Soil types such as sandy/rocky environments, concrete and bitumen pose a real problem making a low-impedance environment difficult, and at worst impossible, to achieve. Add in moisture and environmental changes and the problem is exacerbated.

Unearthed or IT systems are also problematic for RCDs due to lack of an earth-path and the 1st and 2nd fault scenario. Although widely regarded as the safest earthing system, they are not widely used as a result.

The Safe Electrical Technology RVD-E is designed to accompany any RCD/RCBO and provide an additional layer of electrical protection. The company says the device enables enhanced electrical protection within the TN(MEN), TT earthed systems and uniquely IT unearthed systems. Importantly, according to the company, RVD-E enables protection against the IT non-dangerous 1st fault condition, allowing the ‘bird on the wire’ concept to become a reality, effectively removing the human from becoming part of the electrical circuit.

The RVD-E is an electrically connected ‘add-on’ device which detects a voltage leakage of 43 V to frame and when sensed, creates a 33 mA imbalance across the accompanying RCD/RCBO, ensuring simple operation. The RVD is complementary to the RCD in providing protection in high-impedance/compromised earth environments, where the RCD operates in low-impedance earth environments. This provides significant benefits and dovetails well to the ALARP approach to risk management.