Insulation Monitoring

Transformers are often used when building a circuit with an IT earthing system. Because IT circuits float with reference to earth they offer a higher level of operational reliability than the more usual TT or TN circuits, because a first earth fault does not give rise to an immediately hazardous situation. In this case it is not necessary to disconnect the circuit, an alarm will suffice. Isolation monitoring devices are used to generate this alarm. These devices constantly monitor the resistance between earth and the circuit. An alarm is issued when this falls below a specified threshold.  In order to offer an advanced solution in these circumstances EREA collaborate with Dossena, a firm with more than 45 years of experience with this equipment. We distinguish between industrial IT circuits (our SRI3/I2 and SRI3/D2 products) and medical IT circuits (SRI3/H2 product series). You can find more information about isolation monitoring and the difference between the industrial and medical versions here.