SAI-3481D digital motor differential protection device

I. Overview
SAI-3481D digital motor differential protection device for 10kV and below the voltage level of the various system wiring ( ungrounded system , a small current grounding system ) in high-voltage asynchronous motor differential protection , as a medium-sized induction motor ( hundreds of kilowatts or more ) internal fault protection. Can be installed in the switch cabinet in place , but also set the screen installed in the control room. Protection configuration
● differential protection
● ratio differential protection
● non-power protection
Control Function Deployment
● 11 road open into the strong electric remote signal acquisition
● device power failure alarm , emergency signal device , the device alarm signal
● 2 -way pulse input
● 1 -way GPS time

Second, the principle that the protection of
2.1, the differential protection
When the current is greater than either move away from the differential speed off the setting value , the action in the export relays.
Its operating conditions are as follows :

Which is a differential current Id , Isd to determine the value of the differential speed
2.2 , the ratio of the differential protection
The device uses a conventional rate differential principle , action criterion as follows :
| Id | ≥ Iqd time when Ir ≦ Ig
| Id | - Iqd ≥ K1 * | Ir - Ig | When Ir> Ig
Where : Id is the differential current ;
Iqd for the starting current ;
Kzd proportional braking coefficient ;
Ir brake current ;
Ig is the current inflection point ;
Let the motor -side current Ih , Il neutral point of the motor current ;
Then: the differential current Id, braking current Ir calculated according to the following formula
Id = | Ih + Il |
Ir = | Ih - Il | / 2
When the program relative to discrimination by any one phase to meet the above criterion action , the differential action , action characteristics as shown below.

Its action logic is as follows :

2.3, CT disconnection alarm and lockout
1) CT break blocking or warning :
After starting rate differential , subject to disconnection of CT testing to ensure the flow is not due to poor break caused . CT is determined after the break , delay 2 seconds an alarm signal , reporting CT disconnection, by adjusting the control word can decide whether locking differential protection .
CT disconnection determining when any of the following conditions are satisfied , the determination is not performed CT disconnection :
a) before the start of a side of the maximum phase current is less than 20% of the rated current is not sentenced to the side ;
b) After the start phase current is greater than 110% of the maximum rated current ;
c) he served as a starting phase current increase over the previous start.
In the case of the above three conditions are not met, such as one side of the following conditions are satisfied , the penalty for CT disconnection :
a) there is a zero -phase current ;
b) The remaining before the start of the two-phase currents and currents are equal.
2 ) differential current limit alarm :
If the difference is greater than 25% of the flow differential current setting , by discrimination over 10s
After an alarm signal. And reports differential current -limit , but not locking differential protection . CT disconnection criterion function as both the AC sampling circuit protection device monitoring function and a small load situations. 2.4 , non-power protection
Come from non-electric motor body contact, to switch the device input terminals , the trip or not is determined by the soft platen. Such as soft platen exit , only for ordinary credit away , otherwise it will jump all the switches accordingly . After the device trips, event logging , and MMI will be recorded by the computer to upload to the background .
2.5 , data record
Function with SAI-318D, analog can be recorded as Iah, Ibh, Ich, Ial, Ibl, Icl, Icda, Icdb, Icdc.
2.6 , remote telemetry, remote control
Function with SAI-318D.

Third, the setting and press apparatus
3.1 , setting the value of a list and description of
No. Name Symbol Range Unit Remarks
A control word KG1 0000 ~ FFFF no see control word description
2 Rated current Ie 0.2 ~ 15.0 A
3 Starting current Iqd (0.2 ~ 1.2) Ie A
4 inflection current Ig (0.8 ~ 1.2) Ie A
5 braking coefficient Kzd 0.1 ~ 0.9
6 differential current Isd (2.0 ~ 15) Ie A
Control word definition:
Meaning Bit 0 is set to 1 when the meaning set
15 CT rated current of 1A CT rated current of 5A
4 to 14 Reserved Reserved
3 motor starter motor to start discriminating judgment into exit
1 CT CT disconnection is not broken locking differential locking differential
0 differential current limit alarm input differential current limit alarm exit
3.2 , soft list and description of the platen
Corresponding function name plate
Differential protection differential protection function cast back
Differential speed differential protection cast back
Non-electricity a non-power protection features a cast back
Non-power consumption 2 2 Non- return investment protection
Non-power consumption 3 3 Non- return investment protection