This innovative, safe, and highly cost-effective solution is designed to remotely display the presence/absence of voltage on a bus bar. The system is composed of two devices connected by optical fibre cable: 1. voltage detecting system 2. relay for remote indication The VDS, in accordance with IEC61243-5, continuously detects and indicates voltage. Blinking LED’s on front show the live phases while transmitting optical signals to the relay. Optical fibre cable provides galvanic isolation between medium and low voltage sections. The blinking of the LED’s can also be used for optical phase comparison as it is synchronous and coherent with medium voltage. The remote indication relay, with double changeover contacts, displays voltage presence or absence locally. It also allows users remotely to monitor voltage on the bus bar, which is used to implement logic protection. Optical cable provides a great advantage, guaranteeing complete insulation. Even if a capacitive divider fails, no damage or discharge to the low voltage compartment will occur. Typical applications include, automatically switching from standard power to emergency, or prevention of ground faults.