Voltage transformers for railways
Description and application
DESCRIPTION: The transformer cores are made of high-quality cold-rolled magnetic steel sheet with an oriented crystal structure. The primary and secondary windings are cast in epoxy resin filled with quartz sand, resulting in an electrically and mechanically very robust construction. A special structural solution for the windings ensures a uniform distribution of lightning impulse overvoltages along the windings and over the surface of the insulating part of the transformer. Due to all these characteristics, and despite their small dimensions, these transformers excellently withstand tests with an induced overvoltage of increased frequency and tests with lightning impulse overvoltages.
Since the core is made of very high-quality magnetic steel sheet (low specific core losses), even at high magnetic inductions that can occur in the event of an earth fault on an ungrounded network in single-pole insulated transformers, there is no danger of impermissible heating of the transformer core. Single-pole insulated voltage transformers can also be executed with an auxiliary winding (tertiary winding) for open-delta connection intended for earth-fault protection in three-phase networks. An ohmic resistance (resistor) in the open-delta winding circuit of three single-pole insulated voltage transformers connected in a star configuration in networks with an isolated neutral point prevents the occurrence and maintenance of ferroresonant phenomena, which can arise during transient operating conditions of the network. We manufacture voltage transformers for all climatic conditions.
APPLICATION: Measuring voltage transformers are used to isolate measuring and protective devices from high voltage and to transform the voltage to a value adapted to the measuring and protective devices. Transformers intended for installation in networks supplying railways are produced as single-pole insulated for indoor installation with the highest voltage for equipment up to 42 kV, and for outdoor installation with the highest voltage for equipment up to 52 kV.
The accuracy class of the voltage transformer should be selected according to its purpose:
- Class 0.2: for laboratory measurements and test stations, for the most accurate power measurements in operation, and for measuring electrical energy consumption for billing at large consumers;
- Class 0.5: for operational voltage and power measurements, for measuring electrical energy consumption, and for supplying auxiliary relays;
- Class 1: for cases where a large rated power output is required, and a higher accuracy class is not necessary;
- Class 3P, 6P: for supplying electrical protective relay devices.
Installation, versions and maintenance
INSTALLATION: Epoxy-insulated voltage transformers JNTSM-36 for indoor installation and NMTSM-38 for outdoor installation are mounted in a vertical position. The primary terminals of single-pole transformers are connected between phase and earth. All metal parts of the transformer that are not live under normal conditions but can become live in the event of a fault must be earthed. A fixing strap marked with the earthing symbol is located on the transformer. Depending on the measuring connection, one secondary terminal is also earthed. For single-pole insulated voltage transformers, the secondary terminal n is earthed, as well as the primary terminal N.
The secondary terminals of a voltage transformer may be open in operation or loaded with small consumers of high resistance (voltmeters, voltage circuits of meters and relays). The secondary terminals must never be short-circuited, as this would cause the destruction of the voltage transformer. Therefore, secondary lines are usually protected with fuses. Earthed conductors are not fused. The permissible tightening torque value Mp on the high-voltage (HV) terminals with an M10 bolt is 24.5 Nm, and with an M16 bolt is 98 Nm.
VERSIONS: We manufacture transformers for indoor and outdoor installation with one or two secondary windings. For indoor installation, there are also variants with high-voltage fuse holders, allowing these fuses to be integrated directly into the transformer.
HANDLING AND MAINTENANCE: Regular maintenance is not mandatory for these transformers. From time to time, the transformers should be wiped down (cleaned), especially if they operate in aggressive or dirty environments. Wiping of the transformers must be performed in a de-energized (dead) state. In the event of breakdowns in the plant, it should be tested whether the transformers are still operational.
Voltage transformers for railways
Voltage: 25 kV, 27.5 kV, 35 kV | Mounting: Outdoor / Indoor | Insulation: Cycloaliphatic resin / Epoxy resin
Single-pole insulated transformers with one or two secondary windings.
Highest voltage for equipment up to 42 kV for indoor mounting and up to 52 kV for outdoor mounting.
Voltage transformer for outdoor mounting
JNT SM-36-10R
Mounting: Outdoor | Voltage: 25 kV | Highest voltage for equipment: 42 kV
| TECHNICAL DATA | JNT SM-36-10R |
|---|---|
| Rated primary voltage (kV) | 25 |
| Highest voltage for equipment (eff.) (kV) | 42 |
| Lowest operating voltage (kV) | 19.5 |
| Highest operating voltage (kV) | 29 |
| Creepage distance (mm) | 1280 |
| Mounting | Outdoor |
| Rated frequency (Hz) | 50/60 |
| Rated transformation ratio (kV/kV/kV) | 25/0.1/0.1 |
| Secondary winding (1) - rated voltage (V) | 100 |
| Rated power and accuracy class for the secondary winding (1) | 30VA; class 0.5 |
| Secondary winding (2) - rated voltage (V) | 100 |
| Rated power and accuracy class for the secondary winding (2) | 60VA; class 1 |
| Rated power-frequency withstand voltage, 1min (kV) | 95 |
| Impulse voltage 1.2/50µs (kV) | 200 |
| Mass (kg) | 43 |
| Temperature class of insulation | E |
| Type of basic insulation | Cycloaliphatic resin |
| Valid standards | IEC 61869-1; IEC 61869-3 |
Single-pole measuring voltage transformer
DNT SM-36-10R1
Mounting: Outdoor | Voltage: 25 kV or 27.5 kV | Highest voltage for equipment: 40.5 kV
| TECHNICAL DATA | DNT SM-36-10R1 | |
|---|---|---|
| Mounting | Outdoor | |
| Transformation ratio [kV/kV/kV] | 25/0.1/0.1 | 27.5/0.1/0.1 |
| Rated voltage [kV] | 25 | 27.5 |
| Highest voltage for equipment [kV] | 40.5 | |
| Secondary winding (1) - rated voltage [V] | 100 | |
| Rated power and accuracy class for the secondary winding (1) | 30VA ; 75VA / class 0.2 ; class 0.5 | |
| Secondary winding (2) - rated voltage [V] | 100 | |
| Rated power and accuracy class for the secondary winding (2) | 60VA ; 100VA / class 1 ; class 3P | |
| Rated frequency (Hz) | 50; 60 | |
| Rated power-frequency withstand voltage, 1min [kV] | 80 | |
| Rated withstand impulse voltage 1.2/50µs [kV] | 190 | |
| Creepage distance [mm] | 1320 | |
| Type of basic insulation | Cycloaliphatic resin | |
| Valid standards | IEC 61869-1; IEC 61869-3; EN 50152-3-3 | |
| Mass (kg) | ~64 | |
Single-pole power voltage transformer
DNT SM-36-10R1
Mounting: Outdoor | Voltage: 25 kV | Rated power: 1.5 - 4 kVA
| TECHNICAL DATA | DNT SM-36-10R1 |
|---|---|
| Rated power [kVA] | 1.5; 2; 2.5; 3; 4 |
| Transformation ratio [kV/kV] | 25/0.22 |
| Highest voltage for equipment [kV] | 52 |
| Maximal operating voltage [kV] | 40.5 |
| Lowest operating voltage [kV] | 19 |
| Rated frequency (Hz) | 50/60 |
| Rated power-frequency withstand voltage, 1min (kV) | 80 |
| Rated withstand impulse voltage 1.2/50µs [kV] | 190 |
| Mounting | Outdoor |
| Creepage distance (mm) | 1320 |
| Type of basic insulation | Cycloaliphatic resin |
| Mass (kg) | 60-70 |
| Valid standards | IEC 61869-1; IEC 61869-3 |
Winding voltages
| Connections | Voltage | |
|---|---|---|
| Rated primary voltage [V] | A-N | 25000 |
| Rated secondary voltages [V] | a1-n | 209 |
| a2-n | 220 | |
| a3-n | 231 | |
| a4-n | 242 | |
| a5-n | 253 |
Voltage transformer for outdoor mounting
NMTSM-38
Mounting: Outdoor | Voltage: 35 kV | Highest voltage for equipment: 52 kV
| TECHNICAL DATA | NMTSM-38 |
|---|---|
| Rated primary voltage (kV) | 35 |
| Highest voltage for equipment [kV] | 52 |
| Mounting | Outdoor |
| Rated frequency (Hz) | 50; 60 |
| Rated transformation ratio (kV/kV/kV) | 35/0.1/0.1 |
| Secondary winding (1) - rated voltage (V) | 100 |
| Rated power and accuracy class for the secondary winding (1) | 30VA; class 0.5 |
| Secondary winding (2) - rated voltage (V) | 100 |
| Rated power and accuracy class for the secondary winding (2) | 60VA; class 1 |
| Rated power-frequency withstand voltage, 1min (kV) | 95 |
| Rated withstand impulse voltage 1.2/50µs (kV) | 250 |
| Creepage distance (mm) | 1329 |
| Mass (kg) | ~82 |
| Temperature class of insulation | E |
| Type of basic insulation | Cycloaliphatic resin |
| Valid standards | IEC 61869-1; IEC 61869-3 |
Voltage transformer for outdoor mounting
NMT-1-25
Mounting: Outdoor | Voltage: 25 kV | Highest voltage for equipment: 36 kV
| TECHNICAL DATA | NMT-1-25 |
|---|---|
| Highest voltage for equipment (eff.) (kV) | 36 |
| Rated primary voltage (kV) | 25 |
| Rated secondary voltage (V) | 100 or 403 |
| Rated power-frequency withstand voltage, 1min (kV) | 70 |
| Rated impulse withstand voltage 1.2/50 µs (kV) | 170 |
| Rated frequency (Hz) | 50 |
| Secondary power (VA) for accuracy class 0.5 | 10 |
| Secondary power (VA) for accuracy class 1 | 20 |
| Thermal limiting power (VA) | 600 |
| Mass (kg) | ~60 |
| Temperature class of insulation | E |
| Type of basic insulation | Cycloaliphatic resin |
| Valid standards | IEC 61869-1; IEC 61869-3 |
Voltage transformer for indoor mounting
JNT-36
Mounting: Indoor | Voltage: 25 kV | Highest voltage for equipment: 36 (42) kV
| TECHNICAL DATA | JNT-36 |
|---|---|
| Rated primary voltage (kV) | 25 |
| Highest voltage for equipment (eff.) (kV) | 36 (42) |
| Maximum operating voltage (kV) | 29 |
| Lowest operating voltage (kV) | 19.5 |
| Power-frequency withstand voltage 50 Hz, 1 min (kV) | 70 (95) |
| Rated impulse withstand voltage 1.2/50 µs (kV) | 170 (200) |
| Rated frequency (Hz) | 50/60 |
| Rated transformation ratio (kV/kV/kV) | 25/0.1/0.1 |
| Secondary winding (1) - rated voltage (V) | 100 |
| Rated output and accuracy class of secondary winding (1) | Up to 30VA; class 0.5 |
| Secondary winding (2) - rated voltage (V) | 100 |
| Rated output and accuracy class of secondary winding (2) | Up to 60VA; class 1 |
| Type of mounting | Indoor |
| Mass (kg) | 40 |
| Insulation temperature class | E/B |
| Type of main insulation | Epoxy resin |
| Valid standards | IEC 61869-1; IEC 61869-3 |