Application Guide - NP900 Series
296 (504
)
A996A
Table 3.4.4.5-195. Event codes of the VOC function.
In the register of the VOC function is recorded start, trip or blocked “On” event process
data. In the table below is presented the structure of VOC function register content. This
information is available in 12 last recorded events for all provided instances separately.
Table 3.4.4.5-196. Register content.
Date & Time
Event
code
Fault
type
Trigger
current
Fault
current
Prefault
current
Trip time
remaining
Used
SG
dd.mm.yyyy
hh:mm:ss.mss
6784-
6789
Descr.
L1-G…
L1-L2-
L3
Start
average
current
Trip
-20 ms
averages
Start
-200 ms
averages
0 ms -
1800 s
1 - 8
3.4.5
V
OLTS
-
PER
-H
ERTZ OVER EXCITATION
(24)
Generators, transformers, and motors have a specific volts-per-hertz ratios under which
these machines are expected to operate. If the V/Hz ratio is exceeded, result is machine
overexcitation which causes generators and transformers iron core saturation which will
result in breakdown of core inter-lamination insulation due to excessive voltage and eddy
current heating. Also stray flux will be induced into non-laminated components which are
not designed to carry flux caused currents. For generator overexcitation typically occurs if
the V/Hz ratio exceeds 5% of the nominal V/Hz ratio and the possible damage may
happen within seconds. Most common situation for overexcitation to the machine is when
it is off-line prior to synchronization.
V/Hz protection is based into the ratio of maximum phase to phase voltage and measured
system frequency calculated ratio. Both inverse and definite operating characteristics can
be applied simultaneously for the V/Hz protection.
Blocking signal and setting group selection controls the operating characteristics of the
function during normal operation.
Outputs of the function are Start Trip and Blocked signals. Setting parameters are static
inputs for the function which are changed only by user input in the setup phase of the
Event
Number
Event
channel
Event block name
Event
Code
Description
Event
Type
Alarm
Type
6784
106 VOC1
0 Start ON
1
0
6785
106 VOC1
1 Start OFF
0
0
6786
106 VOC1
2 Trip ON
1
1
6787
106 VOC1
3 Trip OFF
0
0
6788
106 VOC1
4 Block ON
1
0
6789
106 VOC1
5 Block OFF
0
0