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Personal injury or death can result from high voltage. When power generation equipment must be in operation to make tests and/or adjustments, high voltage and current are present. Improper test equipment can fail and present a high voltage shock hazard to its user. Make sure the testing equipment is designed for and correctly operated for high voltage and current tests being made. When servicing or repairing electric power generation equipment:
Failure to do so could result in personal injury or death. Make sure residual voltage in the rotor, stator and the generator is discharged. |
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Accidental engine starting can cause injury or death to personnel working on the equipment. To avoid accidental engine starting, disconnect the battery cable from the negative (-) battery terminal. Completely tape all metal surfaces of the disconnected battery cable end in order to prevent contact with other metal surfaces which could activate the engine electrical system. Place a Do Not Operate tag at the Start/Stop switch location to inform personnel that the equipment is being worked on. |
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| Illustration 1 | g00992028 |
Note: The generator should be connected with the terminal lugs on top of each other. Refer to Illustration 1.
Generator Leads To Terminal Strips
Attach the generator leads to terminal strip in the following manner:
- When more than one lead attaches to the bus bar, place the leads on each side of the bus bar. Use flat plated washer under the bolt head and under the nut.
- After connecting the leads to the bus bar, group all generator phase leads together. Tie these leads together.
Ensure that there is a minimum clearance of 25 mm (1.0 inch) between connections that are not insulated. The connections include phase to phase and phase to ground.
Grounding the Frame
In any generator set installation, the frame of the generator must be connected to an earth ground or to the hull of a vessel. This connection is the first connection that is made at the installation. This connection is the last connection that should be removed. If the generator set is on flexible mounting pads, the ground connection must be flexible in order to avoid possible breakage in later operation.
Ground connection cable or straps must be sized to meet accepted codes and regulations. Joints in cables or straps must be clean, free of electrical resistance, and protected from possible oxidation. Bolted ground connection joints eventually oxidize. The joints are frequent sources of Radio Frequency Interference (RFI). Joints that are silver soldered and bolted are preferred.
Neutral Connections
The generators with a "Wye" configuration usually have the neutral grounded when the generator is installed. Grounding the neutral is for preventing damage to equipment.
If the neutral wire is grounded and one of the phase leads becomes grounded, the excessive current will open a load circuit breaker. Also, the excessive current will cause the generator voltage to collapse. The result depends on the following items: electrical characteristics of the generator , type of fault and trip rating of the circuit breaker. An undervoltage device may be required in order to provide an adequate short circuit protection.
There are some cases when the neutral wire is not grounded. An ungrounded generator neutral lead is acceptable when the possibility of grounds to the phase leads has been eliminated. For example, grounding a neutral wire is not required if ground fault protective circuitry is used. Ground fault protection requires the entire group of distribution circuits to be treated as a system. The owner should contact a certified consultant if a new distribution system is being developed. The owner should also contact a certified consultant if an existing system should be modified for the ground fault protection.
In a three-phase, four-wire system, the neutral wire should be grounded according to local wiring codes.
Be sure to check your local wiring codes.