SAI-3483D digital motor protection devices

I. Overview
SAI-3483D digital motor protection devices for 10kV and below the voltage level of the various system wiring ( ungrounded system , a small current grounding system ) integrated protection in high voltage asynchronous motors, asynchronous motors as a medium to large ( hundreds of kilowatts above ) internal fault , overload protection , etc. . 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
● reflect the speed off phase fault protection
● reflect Stall overcurrent protection
● Overload protection ( alarm , trip )
● Start time is too long to protect
● unbalance protection ( including off -inverting and inverting ) : definite time or inverse time negative sequence overcurrent protection
● Thermal protection ( overheat trip , overheating alarm , heat accumulation memory function )
● Low Voltage Protection
● Over Voltage Protection
● non-power protection
● ground protection ( zero sequence overcurrent protection can trip or signal tuning , selectable definite time or inverse time )
● F-C overcurrent latch
Control Function Deployment
● 11 road open into the strong electric remote signal acquisition
● device power failure alarm , emergency signal device , the device alarm signal
● breaker remote control division , division and frequency statistics
● analog telemetry : Ia, Ib ( optional , must specify when ordering ), Ic, Ua, Ub, Uc, P, Q,, COSθ, F
● power metering
● 2 -way pulse input
● 1 -way GPS time

Second, the principle that the protection of
As a result of the 32-bit microprocessor computing performance greatly improved, the device uses various methods to calculate real-time protection components, is no longer set up a special boot components, all components are calculated in real time , relatively simplified protection logic , in order to facilitate improved the overall reliability of the protection device
2.1 Start-up time element
Means for measuring motor starting time Tstart method : When the maximum phase current of the motor from zero mutation move 10% Ie start counting until after excessive peak starting current drops to 120% Ie when the last date, is called the Tstart. (Ie is the motor rated current. ) Motor starting time is too long will cause the rotor to overheat, start-up time when the actual measurement device exceeds the allowable start time setting Tstart, protective action on the trip .

2.2 differential protection
When the current is greater than either move away from the differential speed off the setting value , the total exports of the relay action .
Its operating conditions are as follows :

Which is a differential current Id , Isd to determine the value of the differential speed
2.3 , the ratio of the differential protection
The device uses a conventional rate differential principle , action criterion as follows :
| Id | ≥ Icd time when Izd ≦ Ig
| Id | - Icd ≥ K1 * | Izd - Ig | When Izd> Ig
Id for the differential current ;
Icd for the differential protection setting value ;
K1 is proportional braking coefficient ;
Izd for the braking 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, Izd braking current calculated according to the following formula
Id = | Ih + Il |
Izd = | Ih - Il | / 2 program by phase discrimination , any more than one phase action to meet the criterion of the differential action , action characteristics as shown below.

Description : This device is not considered disconnection CT , CT break also means that ruled fault .
Differential current limit alarm , just send an alarm signal to the alarm given half the value of the differential value , the time is 10 seconds ( via control word cast back ) .
Its action logic is as follows :

2.4 , overheat protection devices
Considering the motor is positive, the thermal effect generated by the negative sequence current , the motor load caused by superheating of various protection , short-circuit and as a motor start-up time is too long, such as back- stall .
Equivalent to simulate the current Ieq- heating effect of the motor, namely:

Where : Ieq- equivalent current
I1- positive sequence current
I2- negative sequence current
K1- positive sequence current heat coefficient , the motor during startup K1 = 0.5, start the restoration is completed K1 = 1
K2- negative sequence current heat coefficient , K2 = 3 ~ 10, desirable K2 = 6
According to the heating characteristic curve of the motor model , the operation of the motor operating current and the equivalent time t between Ieq is given by the following equation :

Where: Ip- load current before overload if the overload is cold front , then Ip = 0
I ∞ - starting current , that protection is not required for operation of the provisions of the current limit
the time constant τ- reflecting capacity of the motor overload
This criterion is fully considered the motor stator and thermal process state before the load is too hot . Device to indicate the heat content of the motor is proportional to the square of the heat , the heat content of the stator current , by conversion, into its dimensionless motor overload capacity reflects the time constant τ. When the heat content value reaches τ, the device is tripped . When the heat content of Ka × τ, hair overheat alarm signal , which , Ka is a warning factor , which ranges : thermal alarm can be set to heat accumulation whole trip ( 60 to 99.9 ) % , the device provides real-time heat accumulation value display , alarm indication lights and signal contacts output.
According to the principle of the motor can be started twice in a row , each time you start the trip 50% of its value should not be greater than the heat accumulation , so when the heat accumulation value drops below 50 percent , closing latching device contacts to return. After tripping overtemperature protection , thermal memory device startup , output contacts have been closed until the heat accumulation value drops below 50 percent , closing latching contacts overheating return , then the motor can be restarted. When an emergency situation requiring immediate start, thermal reversion operation of the device .
Starting current I ∞ rated current Ie can be 1.05 to 1.15 times the setting .
Thermal time constant τ provided by the electrical plant , if the manufacturer does not provide , according to the estimate of one of the following methods :
① If manufacturers provide thermal limit curve or a group of motor load capacity over the data , then calculated as τ:

After obtaining a set of τ small value .
② if known Stall current I and allowed to stall time t, but also by the following formula to estimate τ:

③ calculated as τ:

Where : θe rated motor temperature , K is the starting current multiples , θ0 ​​is the temperature rise of the motor startup , Tstart as motor starting time . Its action logic is as follows :

2.5 , instantaneous protection element
Instantaneous protection by determining the size of the current to achieve, its tuning range (3 ~ 12) Is. Quick break down automatically to protect the motor starting after half finished . That would effectively escape the huge start-up current of the motor, and can guarantee to provide preparedness severe overload caused by the normal starting motor stall protection .
Action time T1 can tuning circuit breakers for motor control tuning time is usually shorter , and time spent tuning the motor contactor control generally longer, choose the setting of 0.3 seconds.
Its action logic is as follows :

Where Ia, Ib, Ic is the phase current , Isn breaking current value for the speed
2.6 , overcurrent protection devices
The overcurrent protection device settings , when the current is greater than the current setting and reaches the setting time, overcurrent exports.
Overcurrent protection automatically exit when the motor is started automatically put into the starting end .

Where Ia, Ib, Ic is a phase current , In the current set
2.7 , overload protection devices
The overload protection device settings , when the current is greater than the current setting and reaches the setting time via the control word to select an alarm or trip . Overload protection automatically exit when the motor starts automatically put into the starting end .

Where Ia, Ib, Ic is a phase current , In the overload value
2.8 , zero sequence overcurrent protection devices
Ground current depends on the motor power system grounding. In ungrounded or high resistance grounded system , the fault current is only a few amperes , resistance grounding system in hundreds of amperes , direct grounding system will be greater in value . For a high level of ground fault current system , if the three-phase current transformers are equipped with zero- sequence current three-phase currents can be achieved . In most cases , in order to detect low ground current , zero sequence current transformer is often necessary to obtain a zero-sequence current. Thus , microprocessor-based motor protection designed for both two-phase current transformer with zero sequence current transformer plus the way , three-phase current transformer can also be a way .
Its action logic is as follows :

Where I0 zero sequence current , I0d zero sequence current value
2.9 , negative sequence overcurrent element
The main negative sequence current protection for a variety of non-ground asymmetry fault , such as: a phase motor phase failure occurred when the size of the negative sequence component failure due to pre- load rate varies , the load rate is greater than 0.7, the sound can cause excessive phase current, and therefore can not effectively protect the asymmetric general protection fault . When the motor is running , due to the asymmetric power supply , there is always a certain degree of negative sequence current, which will not exceed 30% Is, negative sequence protection tuning should be able to escape this negative sequence current , ie 0.3Is tuning . Operation time characteristics selectable two -time characteristics , select definite time and inverse, extremely inverse action equation:

Where : tp is the time factor , the range of ( 0.05 to 1 )
Ip is the negative sequence current setting
I fault negative sequence current
t for the trip time
Note: The setting value multiplied by the value of inverse time as part of the molecules in the above expression , in seconds , tuning range ( 0.4 to 80 ) .
Its action logic is as follows :

Which is negative sequence current I2 , I2d negative sequence current value
2.10 , low voltage protection devices
Low-voltage protection that can not self-starting motor , or in order to ensure the safety of production, does not allow self-starting motor , after the power supply voltage disappears , the action on the circuit breaker trips , the motor is automatically disconnected from the grid . When measuring voltage U when the voltage drops below a given value , and the A, the C -phase current is zero, low voltage protection action.
Its action logic is as follows :

2.11 , 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 .
Its logic is as follows :

2.12 , the data record
Device has a fault recorder function , you can record the input analog , state the amount that can be recorded as a circuit breaker position , closing protection trip command .
To avoid disturbance of the protective system frequent start , resulting in unnecessary data storage , the device recorded data protection only when the action was stored in FLASH RAM ( retentive ) . Otherwise, this data is only stored in RAM ( brownout not maintained ) , can be read by the PC. Recorded wave reports record is 8-50 , the event can be recorded at least 1000 . Data stored in FLASH RAM .
In addition to the data recording device system disturbances , but also recording device operation event status bit input quantitative event , change event and setting alarm events and other devices .

Third, set and event information 3.1 device , a list and description of the setting value
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 rated motor current Ie 0.5 ~ 20.0 A
7 motor starting time Tstart 1 ~ 20S S
8-speed breaking current value Isd 0.2 ~ 100.0 A
9-speed off time Tsd 0.0 ~ 20.00 S
10 overcurrent settings Igl 0.2 ~ 100.0 A
11 overcurrent time Tgl 0.2 ~ 3000 S
Overload setpoint 12 Igfh 0.2 ~ 100.0 A
13 Overload time Tgfh 0.2 ~ 3000 S
14 zero-sequence current value I0 0.04 ~ 5.00 A
15 zero-sequence current time T0 0.0 ~ 20.00 S
16 Negative sequence current value I2 0.2 ~ 100.0 A
17 negative-sequence definite time T2 0.1 ~ 20.00 S
18 negative-sequence inverse time T2fsx 0.4 ~ 80 S uses extremely inverse
19 low voltage setpoint Udy 2.0 ~ 100.0 V line voltage
20 Low voltage operation time Tdy 0.0 ~ 20.0 S
21 over-voltage setpoint Ugy 2.0 ~ 100.0 V -phase voltage
22 low- voltage operation time Tgy 0.0 ~ 20.0 S
23 overheating starting current I ∞ 0.2 ~ 20 A
24 thermal time constant τ 6 ~ 3000 S
25 coefficients of thermal effect of negative sequence current K2 3 ~ 10 generally advisable to 6
26 overheat alarm coefficient Krgj 0.3 ~ 1.0 is generally taken as 70%
Cooling time of 27 multiple Ksr 1 ~ 5 times τ multiple of 4.0 is generally desirable
28 non-power a delay Tfdl1 0.0 ~ 100.0 S
29 non-power two delay Tfdl2 0.0 ~ 100.0 S
30 non-power 3 delay Tfdl3 0.0 ~ 100.0 S
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
14 into motor starter motor starter discrimination discrimination exit
11 to 13 Reserved Reserved
10 non-power capabilities into non-power function exit
9 overload tripping overload alarm
8 CT CT disconnection is not broken locking differential locking differential
7 -phase current of two -phase to three-phase phase current CT CT
6 differential current limit alarm input differential current limit alarm exit
5 PT break into PT disconnection discriminating judgment exit
4 control back into the control back to the disconnection disconnection discriminating judgment exit
3 Negative sequence overcurrent inverse time mode selected negative sequence overcurrent time mode is selected
2 zero- sequence protection vote cast zero sequence protection trip alarms
An overheated latch into latching exit overheating
0 overheat alarm inputs overheat 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
Current speed off current protection feature cast back
Overcurrent overcurrent protection cast back
Ground protective grounding protection cast back
Negative sequence overcurrent cast back negative sequence overcurrent protection
Overheat protection thermal protection cast back
Low voltage and low voltage protection cast back
Over-voltage over-voltage protection cast back
Overload protection Overload feature cast back

BRIEF one : SAI-3483D principle wiring diagram