T&D World Magazine

Transducer Provides Optimum Interface Between Voltage Monitor, Protection Relay

Lindsey Manufacturing Company has introduced the Voltage Monitor Transducer (VMT). This unit provides an optimum interface between Lindsey’s Current and Voltage Monitoring Insulators (CVMI) for overhead and underground voltage and current sensors and electric utility protection relays, metering devices, and other intelligent electronic devices (IEDs).

The first universal device of its kind for electric utility distribution automation (DA) systems, the VMT provides metering-grade accuracy and can be applied to any protection relay. It incorporates three channels in a single package to accommodate typical three-phase voltage monitoring applications. The VMT functions as a unity-gain amplifier, which accepts the voltage signal from a Lindsey, CVMI sensor, and then outputs said voltage at an appropriate power level to drive the voltage input of the protection relay, regardless of the input impedance of the protection device.

According to the Lindsey Marketing Manager Phil Spillane, the VMT opens up a much wider range of distribution protection and automation applications for Lindsey’s cost-effective, high-performance voltage monitors. “In the past, each sensor had to be constructed to exactly match the input impedance of the corresponding IED,” said Spillane. “With the VMT, users can apply our voltage monitors to any protection relay without the need for specialized configuration.”

The VMT has a protection relay burden of greater than 10 k-Ohm, and its wide bandwidth (30 Hz to 4.2 kHz) provides resolution to the 70th harmonic. The compact unit (4 in. wide x 10 in. long x 2 in. high) includes an integral power supply, which accepts 120 VAC, 24 VDC or 48 VDC. Input/output voltage is rated at 120 VAC nominal, with 150 VAC maximum output and 1,000 VAC/VDC maximum input. The VMT’s power outage run-through is >15 cycles; in the event of control power loss, the device’s signal output continues, uninterrupted, for a minimum of ¼ second (does not apply to 48 VDC power).

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