e-VT Guard
eVT Guard Ferroresonance Protection Devices

The e-VT Guard is an active damping device for MV inductive voltage transformers (VTs) that manages instances of ferroresonant over voltage.

The device applies an immediate and effective resistive damping when a ferroresonant event occurs without creating excessive consumption (as is the case when permanent damping resistors are used).

The e-VT Guard connects directly to the secondary terminals of a VT and can be installed on any VT*.

Features

  • Damping resistors are applied to the VT secondary for a short period of time (150 ms). Afterward, they are gradually disconnected to reduce the chance of ferroresonance reignition.
  • LED indicator that blinks every 5 seconds to signal operational device status. The blinking pattern changes every time the damping resistors are applied. The change in pattern allows a visual indication of the number of times the e-VT Guard has detected ferroresonant events in the last 48 hours.
  • Optional 5 second delay for applications with relay protection devices.
  • Digital relay output that can be connected to a controller, meter, or other device capable of receiving the signal. This signal will pulse each time a ferroresonant event is detected.
  • Single phase connection.
  • When only a single relay input is available, the relay contacts of three e-VT Guard units can be connected in parallel and wired to the relay, controller, meter or other device.
  • Indoor and outdoor rated (with the inclusion of the extended junction box cover).
     

Technical specifications

Rated operation voltage Vr 100-130 V
Max operation current Imax 30 A/0.2s
Relay contact voltage Vc 125 V AC (Max. 100 mA)
30 V DC (max. 100 mA)
Nominal frequency fn 50/60 Hz
Optional damping delay td 0s/5s


Operating ambient temperature: -40°C to +75°C 
Storage and transportation temperature: -50°C to +85°C 
Humidity: up to 90%
 

Certifications and standards

The e-VT Guard has an IP20 protection class, IP54 with extended junction box cover.

The e-VT Guard is UL 61010-1 certified.
 

* The e-VT Guard requires connection to secondary voltage taps that are configured for 115V-120V.

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