Download PDF version

Some of the customers have felt that tingling sensation at one time or another, when coming in contact with metallic equipment. But for an electrician, it is a sign that all is not right, especially when the sensation becomes more like a vibration or an intense jolt.

The problem arises from electrons wanting to find a return path to the ground. A common culprit is a stray wire inadvertently touching the metal casing via a high-resistance path that is not of sufficient magnitude to trip a breaker.

stray voltage

When the stray voltage induces a current via a household appliance, it is usually a mild tingling sensation when exposed to it. However, when a high or medium-voltage substation is not designed properly, the results can be catastrophic.

Some simple approaches to mitigate induced stray voltages can be incorporated into a design to prevent injury or death to personnel.

Avoiding Injury or Death

If an energized wire is relatively close to the ground, an induced voltage may exist

In industry, the problem becomes serious when electrical substations are not properly designed to protect personnel from injury or death. Even when overhead wires are as high as 30 feet high, the electrical field is still attempting to find a way to establish a ground path.

If an energized wire is relatively close to the ground, an induced voltage may exist. For the professional engineer designing a proper electrical facility, he/she can consider suitable approaches to mitigate the hazard.

Gradient Control

Gradient control consists of using equipotential planes to maintain safe steps and touch potential levels. With this approach, all conductive objects that could inadvertently come into contact with an energized conductor, are bonded to the same electrical grounding system at a common reference plane.

With a common reference plane, the magnitude of an induced stray voltage can be reduced to a near equipotential level.

Active Suppression

Active suppression consists of a nulling device to counter the stray voltage by delivering a controlled current

Active suppression consists of a nulling device to counter the stray voltage by delivering a controlled current to the earth.

This is accomplished by measuring the stray voltage between a given point and an isolated reference ground, which is then used as an input to a differential amplifier to deliver a specified amount of current to a remote grounding electrode to null out the measured stray voltage.

Impedance Isolation

In specific electrical distribution systems, there may be unintentional current flowing from the utility company’s neutral grounding system to the customer’s neutral grounding system. To protect the integrity of the utility distribution systems and ensure their power reliability, utility companies sometimes intentionally isolate their grounding reference planes from the customer.

Thus, to reduce the stray voltage impact of this, impedance isolation methods, such as a spark gap, a saturable reactor, or a solid-state switch can be used. When properly applied, this technique creates an intentionally higher impedance to restrict the magnitude of the stray voltage on the customer side.

Download PDF version Download PDF version

In case you missed it

Mitsubishi And HD Renewable Partner For Carbon Neutrality
Mitsubishi And HD Renewable Partner For Carbon Neutrality

Mitsubishi Electric Corporation announced that it has signed an agreement with HD Renewable Energy Co., Ltd., a Taipei-based developer and operator of solar power and battery stora...

Delta's IPT-50kVA UPS Enhances Tunnel Safety
Delta's IPT-50kVA UPS Enhances Tunnel Safety

The Westerscheldetunnel, a vital infrastructure asset managed by N.V. Westerscheldetunnel on behalf of the Province of Zeeland, is the longest tunnel in the Netherlands at 6.6 kilo...

TE Expands In Utilities Market With Richards Acquisition
TE Expands In Utilities Market With Richards Acquisition

TE Connectivity plc, a world pioneer in connectors and sensors, has entered into a definitive agreement to acquire Richards Manufacturing Co. from funds managed by Oaktree Capital...

vfd