Service manual

STP 11-25R13-SM-TG
T - 26
i. Never put your hand on or near a capacitor bank or anything attached to a capacitor unless a
hard ground wire has first been attached. In all but less than 1000-Joule capacitors, this has to be
preceded by discharging through a resistive ground. (number of Joules equals 1/2 the capacitance in
farads times the operating voltage squared, J = 1/2CV
2
).
j. When voltages of 500 volts or more are to be measured, the following precautions are to be
observed:
(1) Deenergize the equipment to be tested.
(2) High voltage capacitors, and the terminals to which the test equipment is to be connected, shall
be discharged at least twice, with a minimum 15-second interval, by using suitable insulated shorting or
grounding bar.
(3) Attach a temporary but secure ground to the circuit.
(4) Withdraw from the equipment under test; make sure that you are free from the leads and in a
proper position for taking meter indications correctly.
(5) Do not use hand-held probes. Use only plug-in or clip-on probes that can be attached before
power is applied.
(6) Assign the responsibility of energizing the equipment to assistant standing by the switch.
(7) Do not touch the test instruments while the power is on.
(8) After taking the reading, deenergize the equipment.
(9) Before removing the test leads, discharge high voltage capacitors and the terminals to which
the test equipment is connected at least twice, with a minimum 15-second interval, by using a suitable
insulated shorting or ground bar.
(10) Attach a temporary ground to the terminals to which the test instrument is connected.
(11) Remove the test leads.
(12) Remove the temporary ground.
(13) Repeat the above precautions for each measurement as applicable.
T-34. Grounding Systems.
a. The National Electrical Code has been adopted as a national standard and is now widely
accepted as the minimum requirements of a grounding system to safeguard personnel and property from
electrical hazards. The National Electrical Code handbook is available from the NATIONAL FIRE
PROTECTION ASSOCIATION, 470 ATLANTIC AVE, BOSTON, MA 02210.
b. Grounding systems and their installation will comply with the requirements of the latest edition
of the National Electrical Code as a minimum, in addition to the requirements of this bulletin.
c. Continuity of all grounding conductors within a facility will be established to a grounding
electrode. The resistance measured from the facility most remote grounding point to each grounding
electrode will be 2 ohms or less. Maximum resistance of the grounding electrode to earth will be 25 ohms
or less (Article 250-84, National Electrical Code).