- Sensors
- Temperature monitor TW 50/60
- Temperature monitor TW 03 S – Type 8432
- Electronic temperature monitor – Type 8433
- PT100 thermo sensor – Type 8433
- Electronic thermostat – Type 8434
- PT100 thermosensor – Type 8434
- Electronic thermostat in cable form – Type 8434
- PT100 thermosensor 2-wire and 3-wire cable connection – Type 8434
- Non-contact magnetic switch – Type 8441
- Current sensor – Type 8442
- Non-contact overhead wire contact TLC 4 – Type 8474
- Precipitation sensor – Type 8921
- Precipitation sensor – Type 8921
- Potential monitoring/-protection
- Mobile adjustment and test device – Type 8204
- Potential monitoring devices
- Display unit – Type 8540
- Voltage Monitors
- Voltage Signal Relays
- Potential Protection Devices
- for floating grounds with voltage monitoring – Type 8900
- for floating grounds with voltage monitoring – Type 8900
- for floating grounds with current control – Type 8901
- with low voltage limiter, surge arrester current monitoring and remote clearing function – Type 8901
- with SIEMENS low voltage limiter and surge arrester – Type 8901
- for open earthing with current monitoring and remote clearing – Type 8901
- for floating grounds with current control and LED indicator – Type 8901
- Voltage fuse – Type 8961
- Voltage Limiting Device – Type 8962
- Over Voltage Protector Type PSNP – Type 8963
- R/C combination – Type 8970
- Earthing device – Type 8971
- Special relays
- Switching amplifier
- Temperature monitoring – Type 8435-PT100
- Evaluation unit – Type KAG2
- Evaluation unit – Type 8480
- Evaluation unit – Type KAV1
- Switching amplifier – Type 8582
- Switching amplifier – Type 8582DCW
- Isolating switching amplifier – Type 8583
- Switching amplifier – Type 8586
- Mobile Test Device for non-contact overhead contact line switch
- Cable Monitoring Devices
- Points Heating Systems
- Current Monitoring/-supply
- Cabinets
- Accessories
- Individual Solutions
Description
Protection from contact voltage and corrosion present a particular problem in the case of DC powered railway vehicles. On the one hand, direct electrical currents should not be connected to ground in order to prevent corrosion, but on the other hand, strict electrical separation can result in hazardous voltage potentials between the two areas.
Dangerous contact voltages can occur if these areas are close together. Floating grounds are used to resolve this problem.
Low-voltage limiters – like voltage fuses – connect the different grounds when a threshold is exceeded.
This guarantees that no dangerous contact voltages can occur and that short circuits cannot trigger when different grounds are connected (for detailed information, please refer to DIN EN 50122-1 and DIN EN 50123-5 – VDE 0115 Part 3 and Part 300-5).
A complete solution with voltage fuse is described below. The voltage fuse is controlled over the current flowing through the fuse (for a complete solution including control of the voltage fuse over the potential differences on the fuse, see Brochure 8900).
The arrangement consists of 2 core elements:
1. Voltage fuse type 8960
2. Current relay type 8545.
The voltage fuse operates on he principle of a Zener diode (see Brochure 8960). This is the only way the threshold voltage can be adjusted precisely during manufacture – as opposed to the method of voltage flashover between 2 electrodes.
The voltage fuse is set to a value that is sufficiently below the permissible contact voltage (per DIN EN 50122-1, Section 7.3.3 DC 120 V – VDE 0115 Part 3).
Control of the voltage fuse over the flow of current through the fuse is always recommended when an immediate signal is desired and sufficient current (larger than 15 A) flows through the fuse.
In contrast to voltage control, current control triggers
immediately. Since the signal is only available while the current flows, it should be saved. The memory module including test and acknowledge elements is a part of this complete solution.
To check the actual status of the voltage fuse without removing it, continuity testers are recommended with a tone pitch that reacts in a characteristic manner to voltage drops that deviate from zero on the resistors to be checked. In the installed state lockout voltage fuses with one of their poles on the rail grounding always show a potential difference between their connections that consists of a direct current with a superimposed AC component.
A voltage fuse that has failed in the conductive state cannot demonstrate a potential difference between its connections because the continuity resistance is nearly zero.
Continuity testers that respond to these operating conditions in the manner described above can be used to test installed fuses.
For more information on this system, see “Technical Data” and information in the brochures for current relay type 8545, bi-stable relay type 8587, and voltage fuse type 8960.
Complete solutions are available in many different designs (send us your requirements).
Do you have any questions?
We will be happy to answer you!