How is Generator Grounding Done? - Kaplan Power

Grounding is of great importance when using electrical devices indoors and in residences. Generator grounding is made to protect the electrical installation and to prevent electrical leakages. In the article, information about earthing methods of generators with different features and how they should be used will be given.

Portable generator sets do not have a direct connection with the ground and can be damaged by widening cable connections. Generator sets mostly operate with low short circuit current. This low current is around 3 times the nominal current. Normal size devices cannot provide the energy required for safe generator use.

1. Mobile Generator Sets

For facilities limited to a certain number of KVA, primarily mobile generators are used. These generators do not provide very large amounts of energy and provide energy to a small number of devices. For example, generators are required for places such as stands in markets and grocery stores. Safe and protective conductors must be used when connecting the conductive parts outside the generator set and the conductive equipment parts inside the generator. Each circuit in the generator should be protected with a residual current relay so that it can receive a current less than 30 mA.

If the generator circuit without a residual current circuit breaker is more than one, there must be a residual current circuit breaker for each circuit provided that it is located at a distance of less than 1 meter. There is no generator grounding method in this system and the neutral pole is not accessible. Therefore, this facility will work with the IT grounding method. The devices in which exposed conductor sections must not be connected to a protective conductor are class 2 devices. If the generator feeds the class 2 devices in terms of energy, the exposed conductors cannot connect. However, in these circuits, it may be necessary to include more than one residual current circuit breaker against electric shock inflexible connection cables.

2. Mobile Generator Grounding In Temporary Buildings

Mobile generator grounding in temporary buildings requires the following procedures. Generator sets with higher power and greater than 10 RCCB are required in areas such as construction sites, which are generally used temporarily. The conductive parts in the open parts of the generator set must be connected with protective conductors. To protect the transmission lines in a generator on a single line, a residual current circuit breaker is used provided that it is less than 30 mA. A secondary leakage current protection device can be used for different lines provided that a distance of less than 1 meter is available for differential protection in circuits feeding each other.

In case of failure, the fault current is transferred through the protection conductor. This allows the use of only three-pole devices because it is possible for three-phase loads. The TN-S system is different from the TN-C system. In the TN-S system, neutral conductors are located separately. The circuit must be opened sequentially and with all poles protected by the switching and safety devices. Besides, the neutral section level should not be decreased.

By making special adjustments, the evacuation of the exhaust gases, the installation stages of the generators, and the areas where they are installed are controlled. All these transactions are carried out by applying official procedures. Therefore, it should be performed and controlled by security experts who are professionals in this business.

In temporary buildings, it should be done that all the safety procedures are completed. The most important part of these safety procedures is generator grounding to avoid any electrical leakage situations.

3. Generator Grounding For Generator Sets Installed Once For Settled Facilities

If the facility is stable and a long time is needed for setting, there will be generator grounding process planning. First of all, the stability of the facility and working times are taken into consideration. Besides, the mains feeding to meet the energy needs of the facility must be performed after the insulation. Firstly, the network is isolated from the system. The circuit breaker is operated manually and this circuit breaker is held by the locking system. The circuit breaker serves for separation from the network line.

In systems such as TT, IT, TN, the parts of the generator that are open to external contact must be connected to the grounding in the facility. The neutral part of the generator set is connected to the equipotential connection of the ground and the facility through the local ground connection.

If there is an obstacle to these operations and the neutral part is not accessible, the facility operates as a network. If the neutral part is accessible, this part is connected to the protection circuit belonging to the facility utilizing a protective conductor connected to the neutral part. This process can be connected to the protection circuit with copper cables with a size of 16 square millimeters and ready for any fault condition.

If these processes are carried out, the facility starts to fulfill its duty as a TN-S or TT system. Unfortunately, in TN and IT systems, security is not guaranteed in case of any contact. If the facility is supported by a mobile generator, warning notices should be placed near the connection parts of the generator. Besides, all systems except TN-C must have a residual current circuit breaker.

All the generator sets should be done with safety procedures taken by including all generator grounding processes.

4. Generator Grounding Of Mobile Generator Set for One-Time Supply and Fixed Facility Created While Designing

If planning needs to be made regarding energy situations, an all-pole inverter should be used while the plant is in the design phase, where the energy will be fed from the generator instead of the grid. If TT and IT generator grounding scheme is installed in the built-in facility, the exposed and conductive components of the generator must be included in the connection without considering the neutral grounding process in this facility.

If TN is grounding in this facility, the neutral zone of the generator and the exposed electrically conductive areas should be connected to the conductive parts of the electrical installation in the system.

The highly sensitive residual current protection relay should be used when the high current protection devices in the IT and TN-S system are insufficient. While the residual current circuit breaker to be used is grounded, the neutral part should be located in the generator section (this situation is pictured below).

For every case, residual current protection relay must be included in TT systems. In the toroid sensor, TT, and TN-S systems, it is important to place the phase and neutral conductors or the neutral point on the alternator to the conductor part that connects to the grounding of the electrical installation. This method does not work on the TN-C system.

If the generator set is located in a facility with an efficient and continuous supply, the rule to be followed is the most ideal neutral earthing system in the facility. This creates a situation that can be solved without the need to use the residual current protection relay against post-contact electric shocks.

Generator grounding rules are always important for human life. Therefore, engineering calculations should be done under the scientific approach.

5.Generator Grounding Stationary Generator Sets for Fixed Facilities

The generator grounding system to be used in such cases should use the same system as the normal supply. While the generator set is being installed, the starting energy of the generator should be provided over the normal supply and generator set to prevent short circuits and to avoid electrical leakage. The necessary security procedures should be provided from these systems or TN systems.