Specialty Products
R.C. Snubbers
R.C. snubbers are a passive electrical devices, comprised of appropriately selected resistors and capacitors, which are used for protecting medium voltage power transformers from electrical switching transients. While lightning arresters help protect the transformers from the high voltage spikes that appear on the line after a lightning strike, snubbers are better suited for the more common problem of circuit breaker switching transients. Examples of the switching operation include instances where a circuit breaker switches between transformer primaries, or automatically triggered switching between grid and reserve power.
When a circuit breaker interrupts current flow, an arc develops across its contacts. The rapid current interruption usually occurs somewhere other than the current zero-crossing point, giving rise to a Transient Recovery Voltage (TRV), which has significant high-frequency content. If the transients are at the natural resonance frequency of the system, then there is a possibility of internal oscillatory voltages developing in the primary windings of the transformer. A high turn-to-turn voltage will result, which will lead to damage of the insulation.
The problem is further exasperated with modern vacuum-type circuit breakers, which have shorter distances between contacts. This serves to increase the speed of the interrupting cycle. The transient level and frequency are functions of the physical distance between the breaker and transformer, transformer construction, the type of load being switched, and the switching characteristic of the breaker.
The RC-snubber network lowers the frequency of the transient voltage applied to the transformer primary below the resonance frequency of the circuit. It reduces the development of the oscillatory voltages and provides a low impedance path to ground for the transients.
Snubbers are a low cost means for protecting a transformer against a costly repair and related downtime. In designing medium voltage power systems, it is a good practice to at least leave space for future installation of a snubber network.
| Voltage Class | 2.4kV to 34.5kV (150kV BIL) |
| Frequency | 60Hz (50/60Hz Optional) |
| Fuse | 6A Full Range Current Limiting Fuse |
| Resistor | 20 – 50 Ohm (+/- 10%) Tubular Non-Inductive Resistor |
| Capacitor | 0.13uF, 0.25uF, 0.5uF Surge Capacitor |
| Enclosure Type | Type 1 Indoor |
| Enclosure Finish | ANSI/ASA 61 Grey |
| Mounting | Floor Mounting |
| Warranty | 12 Months (See Warranty and Limitations) |
| Quality System | ISO 9001:2015 Quality Management System |
| Optional Features & Accessories |
|
Instruction Sheets & Manuals
Installation, Operation and Maintenance Manual (English)
Installation, Operation and Maintenance Manual (French)
Other Resources
Photos
Ideally, an RC snubber should be installed as close as possible to the transformer it is designed to protect. For new transformers, if space allows, the snubber can be integrated directly within the transformer enclosure, ensuring a minimal cable length between the snubber and the transformer. In retrofit applications or when a standalone snubber is required, careful attention should be given to minimizing the cable length between the transformer and the snubber to ensure optimal protection.
Since power systems are dynamic and each setup varies, there is no universal recommendation for the maximum acceptable cable length before the snubber’s effectiveness is compromised. A thorough analysis, including Transient Recovery Voltage (TRV) studies, is necessary to assess system-specific parameters and determine how the cable length between the RC snubber and the transformer will affect its performance.
Power systems are inherently dynamic, and each setup differs in terms of load characteristics, equipment ratings, manufacturer specifications, configurations, insulation levels, voltage ranges, and the interconnection of various components.
While standard benchmarks and guidelines exist for designing snubbers, a thorough analysis and Transient Recovery Voltage (TRV) studies are necessary to accurately predict the unique transient voltage levels and frequencies specific to each system. This is due to the fact that no two power systems are exactly alike.
By using the results from TRV studies, the ideal capacitor and resistor values can be sized to enhance the system’s protection.
- Snubber Ground Current Monitoring Circuits
- Distribution, Intermediate or Station Class Surge Arresters
- Voltage Indicators / Glow Tubes
- Type 1, 3R or 4X Enclsoure
- 304 & 316L Stainless Steel Enclosure
- Custom Enclosure Finish (Color)
R.C. snubbers are a passive electrical devices, comprised of appropriately selected resistors and capacitors, which are used for protecting medium voltage power transformers from electrical switching transients. While lightning arresters help protect the transformers from the high voltage spikes that appear on the line after a lightning strike, snubbers are better suited for the more common problem of circuit breaker switching transients. Examples of the switching operation include instances where a circuit breaker switches between transformer primaries, or automatically triggered switching between grid and reserve power.
When a circuit breaker interrupts current flow, an arc develops across its contacts. The rapid current interruption usually occurs somewhere other than the current zero-crossing point, giving rise to a Transient Recovery Voltage (TRV), which has significant high-frequency content. If the transients are at the natural resonance frequency of the system, then there is a possibility of internal oscillatory voltages developing in the primary windings of the transformer. A high turn-to-turn voltage will result, which will lead to damage of the insulation.
The problem is further exasperated with modern vacuum-type circuit breakers, which have shorter distances between contacts. This serves to increase the speed of the interrupting cycle. The transient level and frequency are functions of the physical distance between the breaker and transformer, transformer construction, the type of load being switched, and the switching characteristic of the breaker.
The RC-snubber network lowers the frequency of the transient voltage applied to the transformer primary below the resonance frequency of the circuit. It reduces the development of the oscillatory voltages and provides a low impedance path to ground for the transients.
Snubbers are a low cost means for protecting a transformer against a costly repair and related downtime. In designing medium voltage power systems, it is a good practice to at least leave space for future installation of a snubber network.
| Voltage Class | 2.4kV to 34.5kV (150kV BIL) |
| Frequency | 60Hz (50/60Hz Optional) |
| Fuse | 6A Full Range Current Limiting Fuse |
| Resistor | 20 – 50 Ohm (+/- 10%) Tubular Non-Inductive Resistor |
| Capacitor | 0.13uF, 0.25uF, 0.5uF Surge Capacitor |
| Enclosure Type | Type 1 Indoor |
| Enclosure Finish | ANSI/ASA 61 Grey |
| Mounting | Floor Mounting |
| Warranty | 12 Months (See Warranty and Limitations) |
| Quality System | ISO 9001:2015 Quality Management System |
| Optional Features & Accessories |
|
Instruction Sheets & Manuals
Installation, Operation and Maintenance Manual (English)
Installation, Operation and Maintenance Manual (French)
Other Resources
Photos
Ideally, an RC snubber should be installed as close as possible to the transformer it is designed to protect. For new transformers, if space allows, the snubber can be integrated directly within the transformer enclosure, ensuring a minimal cable length between the snubber and the transformer. In retrofit applications or when a standalone snubber is required, careful attention should be given to minimizing the cable length between the transformer and the snubber to ensure optimal protection.
Since power systems are dynamic and each setup varies, there is no universal recommendation for the maximum acceptable cable length before the snubber’s effectiveness is compromised. A thorough analysis, including Transient Recovery Voltage (TRV) studies, is necessary to assess system-specific parameters and determine how the cable length between the RC snubber and the transformer will affect its performance.
Power systems are inherently dynamic, and each setup differs in terms of load characteristics, equipment ratings, manufacturer specifications, configurations, insulation levels, voltage ranges, and the interconnection of various components.
While standard benchmarks and guidelines exist for designing snubbers, a thorough analysis and Transient Recovery Voltage (TRV) studies are necessary to accurately predict the unique transient voltage levels and frequencies specific to each system. This is due to the fact that no two power systems are exactly alike.
By using the results from TRV studies, the ideal capacitor and resistor values can be sized to enhance the system’s protection.
