The Importance of Ground Fault Protection in Industry
Steve Maurer, IME
In the food processing plant where I cut my electrical teeth, there were ceiling drops for sticker guns to label bagged product. Some of the workers complained about getting shocked off the stainless still bins that held the product. Adding inline GFCIs helped (although some still complained, even when no voltage was present).
Ground faults happen when power accidentally touches ground or a grounded frame - often due to insulation breakdown. This can be especially problematic in damp, wet, and dusty environments since water is conductive – exposing potential dangers if not properly maintained.
It's important for designers and maintenance workers alike to stay extra vigilant with these types of conditions present.
Electrical enclosures are bonded and grounded to protect people from electric shock hazards. By creating a low-resistance grounding path, any ground fault currents will travel back quickly to the source instead of causing high voltage on the frame of equipment. This approach reduces risk by providing greater safety for those around electrical devices in all situations.
What are the types of electrical faults?
Electrical faults can be divided into two distinct types: phase-to-phase and ground faults. Phase-to-phase faults are commonly called short circuits. In this case, an overloaded circuit burns a conductor in two, and “short circuits” directly to ground. This causes the fuse to blow or a circuit breaker to open rapidly.
By the way, most circuit breakers are designed to give some indication of why they open. If the handle fully trips, the circuit has shorted. A half-trip often indicates that the circuit was overloaded by too high of an operating amperage load. Power is interrupted in both situations.
In either case, the cause of the trip should be investigated and repair before restoring power to the circuit.
According to research, a remarkable 98% of electrical issues are classified as the latter. Fuses and most circuit breakers protect against phase-to-phase faults. But they don’t keep workers safe in the event of a ground fault condition.
Therefore, an additional layer such as a ground fault protection relay is required for adequate worker safety.
How do ground fault circuit interrupters (GFCIs) work?
Electrical circuits rely on current to return to its source, and ground-fault relays are there as a safeguard. There are two ways they measure fault currents: zero sequence tracking all three phase conductors' output, or via direct measurement of the neutral connection with earth - even in cases where it is equipped with a resistor. If any deviation from these paths exceeds set limits for enough time, the relay will activate accordingly.
If an imbalance of as little as 4-5 milliamps is detected by the GFCIs transformer, the circuit will open, often withing 1/40th of a second.
For home and most commercial uses, the device used has a fixed rating that cannot be adjusted. Whether the device is a GFCI circuit breaker, receptacle, or portable cord attachment, the setting is fixed and shouldn’t be tampered with.
Routine testing should be done on all devices. While most recommendations are to test monthly, a portable device should be checked every time it’s used.
Commercial and industrial GFCI protection
In residential situations, GFCI protection is pretty straightforward. Protection is provided by either the appropriate receptacles or breakers.
And in industrial climates, it’s the same. Offices are one thing. But in the production areas, particularly in food and beverage processing facilities, you need something more robust. Of course, the main power into the plant is usually GFCI protected with a shunt mechanism.
But individual machines or pieces of equipment may need their own GFCI protection.
GFCI relays are used in these instances. Commercial kitchens, for example, often use a Class A GFCI that can be matched to the amperage of the equipment and are normally used for 208 volt equipment.
However, industrial applications are different. They may require an SPGFCI relay to stay in compliance. A Special Purpose GFCI must meet the requirements defined in UL 943C.
With industrial safety in mind, GFCI classes have been specially tailored to meet the needs of each workspace. Class C GFCIs are best-suited for three wired systems with a line voltage not exceeding 480 V and an instantaneous trip level at 20 mA; meanwhile, heavy duty 600V projects call out for Class D units.
Unlike commercial and residential GFCIs, these industrial units are used without a neutral wire. Additionally, some units are “tunable” to cut down or eliminate nuisance tripping.
Products on the market also include a load ground monitoring circuit, a required feature for Class C and D GFCI devices. Littelfuse’s Industrial Shock Block will trip and provide an alarm if the ground return path is broken. This monitoring circuit includes an extra wire (pilot wire) between the Industrial Shock Block and load.
Ground faults happen when power accidentally touches ground or a grounded frame - often due to insulation breakdown. This can be especially problematic in damp, wet, and dusty environments since water is conductive – exposing potential dangers if not properly maintained.
It's important for designers and maintenance workers alike to stay extra vigilant with these types of conditions present.
Electrical enclosures are bonded and grounded to protect people from electric shock hazards. By creating a low-resistance grounding path, any ground fault currents will travel back quickly to the source instead of causing high voltage on the frame of equipment. This approach reduces risk by providing greater safety for those around electrical devices in all situations.
What are the types of electrical faults?
Electrical faults can be divided into two distinct types: phase-to-phase and ground faults. Phase-to-phase faults are commonly called short circuits. In this case, an overloaded circuit burns a conductor in two, and “short circuits” directly to ground. This causes the fuse to blow or a circuit breaker to open rapidly.
By the way, most circuit breakers are designed to give some indication of why they open. If the handle fully trips, the circuit has shorted. A half-trip often indicates that the circuit was overloaded by too high of an operating amperage load. Power is interrupted in both situations.
In either case, the cause of the trip should be investigated and repair before restoring power to the circuit.
According to research, a remarkable 98% of electrical issues are classified as the latter. Fuses and most circuit breakers protect against phase-to-phase faults. But they don’t keep workers safe in the event of a ground fault condition.
Therefore, an additional layer such as a ground fault protection relay is required for adequate worker safety.
How do ground fault circuit interrupters (GFCIs) work?
Electrical circuits rely on current to return to its source, and ground-fault relays are there as a safeguard. There are two ways they measure fault currents: zero sequence tracking all three phase conductors' output, or via direct measurement of the neutral connection with earth - even in cases where it is equipped with a resistor. If any deviation from these paths exceeds set limits for enough time, the relay will activate accordingly.
If an imbalance of as little as 4-5 milliamps is detected by the GFCIs transformer, the circuit will open, often withing 1/40th of a second.
For home and most commercial uses, the device used has a fixed rating that cannot be adjusted. Whether the device is a GFCI circuit breaker, receptacle, or portable cord attachment, the setting is fixed and shouldn’t be tampered with.
Routine testing should be done on all devices. While most recommendations are to test monthly, a portable device should be checked every time it’s used.
Commercial and industrial GFCI protection
In residential situations, GFCI protection is pretty straightforward. Protection is provided by either the appropriate receptacles or breakers.
Many commercial installations are similar and can use just the GFCI receptacle or breaker. However, in commercial kitchens and similar situations, you may want to give extra protection to a major appliance.
But individual machines or pieces of equipment may need their own GFCI protection.
GFCI relays are used in these instances. Commercial kitchens, for example, often use a Class A GFCI that can be matched to the amperage of the equipment and are normally used for 208 volt equipment.
However, industrial applications are different. They may require an SPGFCI relay to stay in compliance. A Special Purpose GFCI must meet the requirements defined in UL 943C.
With industrial safety in mind, GFCI classes have been specially tailored to meet the needs of each workspace. Class C GFCIs are best-suited for three wired systems with a line voltage not exceeding 480 V and an instantaneous trip level at 20 mA; meanwhile, heavy duty 600V projects call out for Class D units.
Unlike commercial and residential GFCIs, these industrial units are used without a neutral wire. Additionally, some units are “tunable” to cut down or eliminate nuisance tripping.
Products on the market also include a load ground monitoring circuit, a required feature for Class C and D GFCI devices. Littelfuse’s Industrial Shock Block will trip and provide an alarm if the ground return path is broken. This monitoring circuit includes an extra wire (pilot wire) between the Industrial Shock Block and load.
Photo courtesy of Littelfuse
