Siemens 7SR242 Duobias - Definite Time (59 NDT); Inverse Time (59 NIT)

7SR242 Duobias Commissioning & Maintenance Guide
©2010 Siemens Protection Devices Limited Chapter 6 Page 42 of 57
2.10.1 Definite Time (59NDT)
If DTL setting is small, gradually increase single phase voltage until element operates.
If DTL is large apply 0.9x setting, check for no operation, apply 1.1x setting, check operation
Apply 2x setting voltage if possible and record operating time
Phase Vs
(Volts)
DTL
(sec)
P.U. Current
Volts
Operate Time
2 x Vs
NOTES
V
1
(V
X)
Check correct indication, trip output, alarm contacts, waveform record.
2.10.2 Inverse Time (59NIT)
It will be advantageous to map the function being tested to temporarily drive the relevant Pickup output in the
Pickup Config sub-menu in the Output Config menu as this will allow the Pick-up LED to operate for the function.
Gradually increase voltage until Pickup LED operates.
Apply 2x setting voltage and record operating time,
Apply a higher multiple of setting voltage and record operating time.
Compare to calculated values for operating times from:
()
[]
⎥
⎦
⎤
⎢
⎣
⎡
−
=
1
1
)sec
Vs
Vn
op
Mondst
Where M = Time multiplier and Vn/Vs = multiple of setting.
Operate Voltage Operate Time
Ph. Vs
(V)
TM
P.U.
(Volts)
D.O.
(Volts)
2 x Vs
(sec)
x Vs
(sec)
NOTES
V
1
(V
X)
2.10.2.1 Element Blocking
The Neutral Overvoltage elements can be blocked by Binary Input Inhibit. This functionality should be checked.
Element BI Inhibits
59NIT
59NDT
Check correct indication, trip output, alarm contacts, waveform record.
When testing is complete reinstate any of the disabled functions.