Volume-II of IV - GAIL

limit feature shall be provided in this mode of operation. The current limit
(Ips) shall be continuously adjustable from zero to rated output current.
b) Auto Mode
In this mode of operation the out put of the CPPSM shall operate in an
external closed loop with pipe-to-soil potential (PSP) in feed back loop.
The CPPSM shall adjust the output voltage so that the PSP as measured
by reference cell always remain equal to the set potential. The set
potential (Vps) shall be continuously adjustable over the specified range.
CPPSM shall be designed to operate with the number of reference cells (to
be provided by others) as specified in data sheet. In case of more than
one reference cell being provided, CPPSM shall automatically select the
reference cell having less negative potential than the others use the same
for CPPSM auto control (e.g. (-) 0.8 V is less negative than (-) 0.9 V).
In case of open circuit or short circuit or potential being less negative than
a minimum set potential (Vrs) for the controlling reference cell, the CPPSM
shall sense these conditions as reference cell failure and shall
automatically switch over to the other healthy reference cell for control.
Should a fault occur in all the reference cells, the output current of the
CPPSM shall adjust automatically to a preset value (Ips) which shall be
adjustable.
In no case shall the maximum PSP be allowed to exceed the specified
maximum potential in any combination of circumstances. (The maximum
potential is the maximum PSP measured by any of all the connected non
faulty ref. Cell).
5.2 CPPSM shall continuously monitor the PSP and necessary annunciation
shall be provided in case of PSP either exceeding the specified maximum
limit (Vpm) or remaining lower than the specified minimum limit (Vpn).
5.3 CPPSM shall operate on a switching frequency preferably above 20 KHZ.
The overall efficiency shall preferably be above 80 %. The output of
CPPSM shall be filtered / smoothened to provide DC output with less than
5 % ripple. Output regulation for no load to full load and with input
voltage variation shall be better than + 5% of the output setting
throughout the range of output voltage and over the specified ambient
temperature variation. CPPSM shall be suitable for ungrounded input
supply system and shall allow grounding of positive terminal of its output.
D:\old data\FATEH\MP Region\Kailaras\Tender RFQ\TCP&PCP\CPPSM-spec.doc Page 5 of 9