!

SAFETY FOR LIFE

S280-79-10

Grounding with a Local Supply Voltage Transformer; 4-Wire Multi-Grounded, 3-Wire Ungrounded, or Impedance-Grounded

Installation of a Form 5 control with a local supply voltage transformer must include the following:

•Protection of the recloser bushings and the supplying transformer with lightning arresters.

•Grounding of the recloser head and tank.

•Grounding of the transformer tank.

•Grounding of the control cabinet.

•Grounding of the SCADA equipment.

IMPORTANT: All external inputs to the Form 5 control must be routed within 8 inches of their corresponding ground. During a surge, a potential of approximately

1.5kV per foot can develop in the conductors. Differ- ences between conductor and ground path lengths can add additional stress to the control components in the event of a power surge.

4-Wire Multi-Grounded Systems

IMPORTANT: In pole-mounted applications, a ground connection must be made between the recloser, transformer, recloser control, and SCADA equipment for proper protection of the equipment. The pole ground must be sized per local utility practices to minimize the impedance between the recloser and the control.

3-Wire Ungrounded and Impedance Grounded Systems

The use of a grounding mat may be required depending upon the local safety regulations defining the permissible step and touch potential levels. Consult local regulations for proper grounding procedures.

Surge

TransformerArrester

Surge

Arrester

AC

NEU

GND

Supply

Voltage

Control

Cable

Pole

Ground

AC

NEU

 

Surge

Supply Voltage

 

 

Arrester

 

 

 

Form 5 LS Control

Input Terminal

 

 

 

 

 

Transformer

Block

 

 

 

 

 

 

AC

 

 

Recloser

 

NEUTRAL

 

 

Head Ground

 

 

 

 

 

 

External

 

 

 

Ground Lug

Arrester Ground

 

ELECTRICAL CONNECTIONS

 

 

 

 

Line to Neutral connected transformer

 

Recloser

 

Supply Voltage

 

 

 

Form 5 LS Control

 

 

 

 

Transformer

Line

 

 

 

AC

Pole

 

 

to

 

 

 

NEUTRAL

Line

 

 

 

 

Voltage

Form 5 LS

 

 

 

Control

Input Terminal

 

 

 

 

Block

External

 

Input

 

 

Ground Lug

 

Terminal

 

 

 

 

Block

ELECTRICAL CONNECTIONS

Line to Line connected transformer

 

Customer Ground Connection

 

At External Lug

 

Figure 29.

Recommended grounding method for the Form 5 Control installed on 4-wire multi-grounded, 3-wire ungrounded, or impedance-grounded systems with local supply voltage transformer.

35