Frequency changes caused by grid voltage fluctuations can lead to unintentional tripping in some relay types. However, Type B relays have an operating frequency between 10 Hz and 1000 Hz, providing high immunity to voltage variations. This characteristic is a crucial factor distinguishing Type B relays from other types, as it prevents nuisance tripping.

In non-harmonic conditions, high-performance Type B relays specifically do not include harmonic filters. You will not find the term 'harmonic filter' in the catalogs of Type F and Type B relays. Adding a low-pass harmonic filter to Type F relays or Type B relays up to 20,000 Hz can eliminate the specific characteristics of these relay types. Therefore, Type B relays are immune to voltage fluctuations, not harmonic currents.

To test a product, you can perform a simple experiment with a machine that has a drive, without needing a complex laboratory. The video below demonstrates an experiment conducted on a machine with 7 drives, featuring an ISKRA Type A (K) harmonic filter relay, a Type B Relay, a Type F relay, and a Type SI relay. This test shows that Type F and Type B relays, when not containing a harmonic filter, cannot operate reliably in a 40 Amp machine.

Type F relays have a wide range of applications and can be used in various scenarios, such as:

• UPS output sockets
• Residential buildings, apartments, villas
• Lighting systems
• Photovoltaic systems
• Electric vehicle charging

These relays can operate without the need for an auxiliary power supply and can be effectively used in systems that do not utilize a neutral conductor. Type B Residual Current Devices, which possess international standard test and quality certificates from Germany, offer a superior solution in terms of reliability and performance.