Electrical Stray Current
Electrical stray current refers to the flow of electrical current via two objects due to potential difference, imbalance or wiring flaws. Small voltage difference between two grounded objects in separate location may exist because of ordinary flow of current within the power system. However, large voltage difference can be a sign of faulty condition in electrical power system.
Have you excessively been shock close to a swimming pool, when you touched the metal installation? Where does it comes from?
Stray Voltage, is a small voltage possibly 10 volts that appears between two contact points. When these two points gets into contact by any mean, a current will definitely flow because of potential difference. This current is Stray Current. The value of stray current depends upon voltage difference and circuit impedance. Stray current can be dangerous, if it flows in considerable amount.
Now the second question arises is that, where does stray voltage originates from?
Due to grounding of electrical power system, any neutral to earth voltage (NEV) on the system can be transmit to any grounded objects. Load, leakage, and fault currents flowing via the impedance’s of the neutral or grounding conductors to earth causes NEV. There are many other sources that lead neutral or grounding system to earth causing NEV. Any metallic structure linked to the neutral or grounding system may also be at the same NEV. This indicates their is constantly voltage to earth. So, the question is not if there’s stray voltage, but what’s the safe level.
How to solve a stray voltage problem?
There are four methods to eliminate or reduce stray voltages.
- Reduce the potential voltage supply to an appropriate level. This includes getting rid of bad neutral connecting and defective loads. Reform grounding, load balancing and clearing leakage current.
- By means of the usage of active nulling devices for elimination of the stray voltage. A current is delivered to a some distance off grounding electrode to null out the measured voltage.
- In some cases, there may be current flowing from the consumer grounded neutral machine to the primary power grounded neutral system. To get rid of and reduce the effect of this, installation of spark gap, saturable reactor or a solid state switch can be used.