Improved safety for accommodation with experimental systems
One of the leading manufacturers of training systems, Elabo TrainingsSysteme GmbH, produces the required protection with SIQUENCE Type B residual current circuit breakers from Siemens.
New criteria for electrical equipment
The criteria for modern electrical and electronic equipment are changing at an ever-increasing rate. Electronic equipment can also generate smoothed residual DC currents. Electronic and electrical engineering laboratories, technical training and experimental systems in training colleges, universities and other technical training systems must theoretically be fitted so that they can, for example, operate with or without transformers. Elabo TrainingsSysteme GmbH, the builder of technical training and experimental systems, fits training systems complying with the latest technical requirements.
The Project: Type B residual current circuit breakers are a must
To detect even smoothed residual DC currents, since June 2007, under the build standard DIN VDE 100-723 (issued June 2005), the use of Type B residual current circuit breakers has been stipulated for rooms with experimental systems to guard against electric shock. The reason for this is: Various types of fault current can occur on experimental positions in technical training establishments and workplaces even smoothed residual DC currents.
The Solution: SIQUENCE Type B from Siemens
Smooth residual DC currents are not detected by Type A residual current circuit breakers for sinusoidal AC residual currents and pulsed DC. Residual DC currents can even lead to Type A residual current circuit breakers failing to guarantee their protective functions even with AC residual currents owing to premagnetising of the transformer.
Siemens was the first manufacturer to introduce the Type B current-sensitive residual current circuit breaker in 1994, and this also detects residual DC currents. The SIQUENCE Type B current-sensitive residual current circuit breaker (RCCB), besides residual AC currents and pulsed DC residual currents, also detects smoothed residual DC currents and thus guarantees the desired protection function with all types of residual current.
All types of residual current under control
SIQUENCE current-sensitive Type B residual current circuit breakers have a supplementary transformer which is loaded with a control signal. This can analyse the change to the transformer duty cycle caused by residual DC currents. This guarantees the desired protection function.
Current-sensitive residual current circuit breakers operate independently of the supply voltage, complying with the current criteria in Germany for Type A according to DIN VDE 0664-100.
A power supply is only needed to detect smoothed residual DC currents by means of a second transformer. This is implemented by all power leads and is dimensioned so that the electronics still trip securely even if the voltage falls to 50 V. This provides a solution for smoothed residual DC currents, provided these residual current waveforms can occur even if there are power cuts, for example if the neutral line breaks.
In the highly unlikely event that two live lines and the neutral line have failed and that the remaining intact live line is causing a risk, the pulsed currentsensitive switched supply unit will still take over the disconnection, with its tripping independent of the power supply.
Type B residual current circuit breakers are suitable for use in an AC system upstream of input current circuits with rectifiers. They are not suitable for use in DC systems and in power supplies with an operating frequency other than 50 or 60 Hz.
The Siemens Type B SIQUENCE series of equipment is designed as a residual current circuit breaker for up to 80 A and as a residual current/line protection switch for up to 125 A. Residual current/line protection switches are a combination of residual current circuit breaker and line protection switch in a single unit. Besides personal, property and fire protection, overload and short circuit protection are also covered. The mechanics of the residual current circuit breaker operates the trip unit in the line protection switch, which isolates the circuit.
Udo Urban, CEO of Elabo TrainingsSysteme GmbH, is convinced: Training facilities have the character of a role model. They must conform in every aspect with the state of the art.