AUGUST 2001
APPLICATION AND COMMISSIONING MANUAL
MIT161 RELAY
EASUN REYROLLE LIMITED
1
Issue No
:
2nd Issue
Date of Issue
:
30.08.2001
Department
:
TP-CTS
2
SENSITIVE CURRENT PROTECTION
PROTECTION
STARTER
HEALTHY
TRIP
MIT
161
EASUN REYROLLE INDIA
MIT161 RELAY
3
CONTENTS
PAGE
APPLICATION
5
INSTALLATION
12
COMMISSIONING
18
WIRING DIAGRAM
24
4
APPLICATION
1. INTRODUCTION
The type MIT161 numerical sensitive current protection relay combines the power and
flexibility of microprocessor technology. The relay is especially tuned to suit applications
where low settings, low burden and rejection of harmonic currents become a necessity.
The relay is suitable for high resistance earth fault protection and capacitor bank
unbalance current protection.
2. CHARACTERISTICS
MIT161 relay has two stage protection i.e. earth fault element and lowset element.
Earthfault element is provided with DTL characteristic and the lowset element is provided
with DTL & IDMTL (Standard Inverse 3 sec, Standard Inverse 1.3 sec, Very Inverse
Extremely Inverse and Long Time Inverse) characteristics.
3. RESET TIME DELAY
The lowset element IDMTL characteristic is also provided with reset time delay
characteristic for detecting “Flashing faults”.
The increasing use of plastic cables, both, conventionally buried types and aerial bundled
conductor types have given rise to the number of "pecking" or "flashing intermittent faults
on distribution systems. At the fault position, the plastic melts and temporarily reseals the
faulty cable for a short time, after which the insulation fails again. The same phenomenon
has occurred in joint boxes where an internal flashover temporarily reseals.
The behaviour of different types of over current relays under flashing fault condition is
compared in Fig.1. The repeating process often caused electromechanical disc relays to
"ratchet” up and eventually trip the faulty circuit provided that the reset time of the relay
was longer than the time between successive flashes. Early electronic IDMTL relays with
instantaneous reset features were not at all effective in dealing with this condition and
only tripped after the flashing fault had developed into a solid permanent fault.
To overcome this the MIT161 relay has a reset time setting which can be user
programmed to be either instantaneous or delayed from 1 to 60 seconds in step of 1 sec.
On the other hand, on overhead line networks, particularly where reclosers are
incorporated in the protected system, instantaneous resetting is desirable to ensure that, on
multiple shot reclosing schemes, correct grading between the source relays and the relays
associated with the reclosers is maintained.
5
FAULT
CURRENT
Fault becomes
permanent
Flashing Faults
TRIP
ELECTROMECHANICAL
SLOW RESET
TRIP
STATIC
INSTANTANEOUS RESET
TRIP
NUMERICAL (MIT)
DELAYED RESET
Figure 1 Flashing Fault Protection
4. SYSTEM EARTH FAULT
Distribution Feeder Fault Current magnitude depends upon the amount of fault resistance
and it can vary from reasonable value to a very low value.
MIT161 has two elements, which can be set for IDMTL and SEF protection to get
complete protection for line ground fault.
R
Y
B
MIT
161
Fig. 2. CT Residual Connection.
Fig.2 shows the CT residual connection for detecting earth faults.
6
Fig.3 shows core balance CT connection for sensitive earth fault application.
R Y B
MIT
161
Fig . 3 CBCT Connection
5. CAPACITOR UNBALANCE CURRENT PROTECTION
MVT161 can be used for unbalanced current protection of double star, delta and singlephase capacitor banks.
MIT
161INSTALLATION
Fig .4. Double Star Capacitor Bank Neutral Unbalance Protection.
7
MIT
161
Fig.5. Single phase capacitor bank/ Delta connected bank unbalance protection.
Fig.5. shows single-phase capacitor bank / 3 phase delta connector bank unbalance
protection. When the relay is used for 3-phase delta connected bank unbalance protection,
3 MIT 161 relays have to be used.
6. TECHNICAL INFORMATION
6.1. Rating
1 Amp / 5Amps
6.2. Frequency
50 Hz
6.3. Auxiliary Supply
Nominal Voltage
24 / 30 / 48 / 110V DC
48/110/220 V DC or 110V AC
Voltage Range
18 – 135 V DC
43 – 280V DC
6.4. Settings
Earth fault element
Low set element
Time Multiplier
Reset Time
0.5% to 25% in steps of 0.5%
0.5% to 25% in steps of 0.5%
0.025 to 1.0 in steps of 0.025
0 to 60 sec in steps of 1 sec
8
6.5. Operating Characteristics
Earth Fault element
Definite Time Lag (DTL)
Low set element
Standard Inverse 3 sec (SI3)
Standard Inverse 1.3 sec (SI1)
Very Inverse (VI)
Extremely Inverse (EI)
Long Time Inverse (LTI) or
Definite Time Lag (DTL)
DTL Operating time
0 to 20.00 sec in steps of 0.01 sec
IDMTL Operating Time can be calculated as follows
T =
K x TM
(I/IS) α - 1
Where
I – Fault current
IS – Setting current
TM – Time Multiplier Setting
SI3
SI1
VI
EI
LT1
K = 0.14
K = 0.0613
K = 13.5
K = 80.0
K = 120.0
α = 0.02
α = 0.02
α = 1.0
α = 2.0
α = 1.0
6.6. Accuracy
Starter
Reset
Repeatability
IDMTL Operate Time
DTL Operate Time
104% of setting ± 4%
≥ 94% of setting
± 1%
± 5% or ± 35 m.sec
±1% or ± 35 m.sec.
6.7. Output Contacts
6.7.1. THE RELAY HAS 5 OUTPUT RELAYS
1.
2.
3.
4.
Common trip / alarm relay
Common Starter
Earth Fault operated
Low set operated
2 N/O
1 C/O
1 N/O
1 N/O
9
5. Protection Unhealthy
1 N/C
6.7.2. CONTACT RATING
Carry continuously
Make & Carry
Break
5 A AC rms or DC
20A for 0.2 sec
50W DC with a max. of 300V or 5A DC
L/R ≤ 40msec
6.8. Burden
AC (1 Amps)
AC (5 Amps)
DC (Quiescent)
0.00006VA at 5mA
0.06VA at 250mA
0.00008VA at 25mA
0.2 VA at 1.25A
5W
7. ENVIRONMENTAL
7.1. Temperature
Operating Range
Storage Range
IEC 60068-2-1/2
- 10°C to + 55°C
- 25°C to + 70°C
7.2. Humidity
IEC 60068-2-3
4 days at 40°C and 93% RH
7.3. Transient Over voltage
IEC 60255-5
5KV, 1.2/50µs, 0.5J between all terminals and Earth or between any two terminals
without damage or flashover.
7.4. Insulation
IEC 60255-5
Variation
2.0KV rms for 1 min between all terminals and earth
2.0KV rms for 1 min between Independent circuits
1.0KV rms for 1 min across normally open contacts
7.5. High Frequency Disturbance
2.5KV Common (Longitudinal) Mode
1.0KV series (Transverse) mode
IEC 60255–22–1, Class III
Variation
≤3%
≤3%
10
7.6. Electrostatic Discharge
6KV Contact Discharge
8KV Air Discharge
7.7. Radio Frequency Interference
20MHz to 1000MHz, 10 V/ m
7.8. Fast Transient
IEC 60255-22-2, Class III
Variation
≤5%
≤5%
IEC 60255-22-3, Class III
Variation
≤3%
4KV, 5/50nS, 2.5KHZ repetitive
IEC 60255-22-4, Class IV
Variation
≤5%
7.9. Vibration (Sinusoidal)
IEC 60255-21-1, Class 1
7.10. Shock and Bump
IEC 60255-21-2, Class 1
8. CUTOUT DETAILS
151 x 151mm (2/3 Vedette draw out case)
11
INSTALLATION
1. UNPACKING
On receipt, remove the relay from the carton box in which it was received and inspect it
for obvious damage. It is recommended that the relay is not removed from the relay case.
To prevent the possible ingress of dirt, the sealed polythene bag should not be opened
until the relay is to be used.
If damage has been sustained, please inform Easun Reyrolle Ltd., for necessary action.
2. STORAGE
When the relay is not required for immediate use, it should be returned to its original
carton and stored in a clean dry place.
3. HANDLING
The relay’s electronic circuits are protected from damage by static discharge when the
relay is housed in its case. When relay is withdrawn from the case, static handling
procedures should be observed:
•
Before removing the relay from its case the operator must first ensure that he is at the
same potential as the relay, by touching the case.
•
The relay must not be handled by any of the relay terminals at the rear of the chassis.
•
Ensure that anyone else handling the relay is at the same potential.
As there are no user serviceable parts and adjustable user settings inside the relay, there
should be no requirement to remove any modules from the chassis.
If any modules are removed or tampered with, then the guarantee will be invalidated.
4. MOUNTING
Mount the relay using 2 nos. mounting straps and 1no earth strap. Ensure that an earth
wire is connected to the earth strap from the earth terminal 23. Terminal 23 should be
directly connected to the system ground.
Only settings or trip details can be accessed via the pushbuttons when the cover is fitted.
To change the settings the front cover has to be removed. Sealing arrangement is
provided in one of the four knurling screws fitted on the cover. Sealing can be done using
a sealing wire. Thus mechanical interlock is provided to avoid unauthorized setting
change.
12
5. EQUIPMENT
5.1 Current tap Selection
MIT relays are suitable for 1A or 5A application. However the relays are internally wired
for either 1A or 5A as per the customer requirement. Internal wiring are to be changed
(Faston crimp connections) for changing the relay rating from one to other.
To ensure the current rating (IR) of the relay, check the connection of CT wires connected
to the bottom TB (Terminal Block) at the rear of the chassis as per the following table:
For 1A
Terminal No. Ferrule No. of CT
of TB
wire(Black)
11
11A
For 5A
Terminal No. Ferrule No. of CT
of TB
wire(Black)
11
11B
Following are the steps to change the current rating of the relay from 1A to 5A.
1. Identify 11th terminal from number strip on bottom terminal block at the rear of
the chassis.
2. The black colour wire “11A” is inserted to 11th terminal of TB.
3. First, carefully lift the PVC boot of the wire by means of a tool (like nose
Plier) to expose terminal 11A.
4. Hold the crimp by means of the same tool at the crimp point and lift to remove
from the fixed terminal. Remove the “11B” wire from the terminal parking rack
(fixed on terminal block) and insert the crimp of “11B” wire on to the terminal No.11
by means of the tool. Insert "11A” wire back to the terminal parking rack.
13
Ensure proper insertion of “11B” wire by pulling the wire by hand and the wire
Should not come off the terminal.
5. Push the boot of “11B” wire to completely cover the crimp.
Same procedure in reverse is to be followed to change from 5A to 1A .
5.2. Human Machine Interface (HMI)
The user friendly HMI provided on the front panel has following features:
Six digit, 7 segment LED display (First two digits are Red colour and other four digits are
Green colour). First two digits (Red) displays the main menu or type of fault when
selected for Setting mode or Trip indication respectively. Remaining four digits (Green)
displays Sub menu or "Trip" indication respectively.
2. Green LED
- Protection healthy indication
3. Yellow LED (STARTER)
- Starter indication
4. Red LED (TRIP)
- Trip indication,
5. Red LED (in →Key)
- Sub Menu
6. ↑ Key
- Up scrolling
7. ↓ Key
- Down scrolling
8. × Key
- Enter / Reset / Cancel / To check Version
5.3. How to operate HMI
Remove the front cover by unscrewing the four knurling screws.
Apply DC supply. Terminals 22,24 and 23 are for positive, negative and earth respectively
as per relay rating. When the relay powers up it takes few seconds to complete the selfcheck routing.
Ensure Protection Healthy LED (Green) is ON and
LED display unit. Wait until the
indication goes off.
Press ↑ or ↓ key
indication appears on the
is displayed
Represents MIT 161 relay
Press ↓ key repeatedly scrolls down the Factory setting Main menu in the following order
on the display.
- Earth fault is OFF (
is Main menu and
- Lowset is OFF
14
is sub menu)
6. SETTING INSTRUCTIONS
6.1. Select Characteristics
6.1.1. FOR EARTH FAULT
Pressing ↓key repeatedly get
Main menu, press Submenu → Key , 3mm
LED in the Key Lit to indicate that the Sub menu is activated.
Pressing ↓ key repeatedly the Sub menu will scroll down in the following order on the
display.
- Characteristics 1 is in OFF
- Definite Time Lag (DTL)
By pressing ↑ or ↓ key choose characteristic (DTL) or OFF and press → key. Now the
Submenu LED goes OFF and the Main menu appears on the LED display.
6.1.2. FOR LOWSET
Pressing ↓key repeatedly get
Main menu, press Submenu → Key , 3mm LED
in the Key Lit to indicate that the Sub menu is activated.
Pressing ↓ key repeatedly the Sub menu will scroll down in the following order on the
display.
- Characteristics 2 is in OFF
- Standard Inverse 3 Seconds characteristics.
- Standard Inverse 1.3 Seconds.
- Very Inverse
- Extremely Inverse
- Long Time Inverse
- Definite Time Lag
By pressing ↑ or ↓ key choose the desired characteristic and press → key. Now the
Submenu LED goes OFF and the Main menu appears on the LED display.
6.2. Current Settings
Setting Range: 0.5% to 25% in steps of 0.5% (For Earth fault and Lowset)
6.2.1. EARTH FAULT
Pressing ↓ key repeatedly get
Main menu (represents Earth fault has been set to
10%), press → key (Submenu LED On) to get the Sub menu. Pressing the ↑ or ↓ key,
changes the current setting in 5mA increment or decrement. Upon selecting the desired
setting, once again press the → key (Sub menu LED goes OFF) to return to the main
menu.
15
6.2.2. LOW SET
Pressing ↓ key repeatedly get
Main menu (represents low set has been set to
10%), press → key (Submenu LED On) to get the Sub menu. Pressing ↑ or ↓ key,
changes the current setting in 5mA increments or decrement. Upon selecting the desired
setting, once again press the → key (Sub menu LED goes OFF) to return to the main
menu.
6.3. Time Setting / Time Multiplier setting
If characteristic is selected as Definite Time Lag, the Time setting range is, 00.00 Sec to
20.00 Sec in steps of 0.01Sec.
If characteristic is selected as Inverse curve, the Time Multiplier setting range is 0.025 to
1.000 in steps of 0.025
6.3.1. EARTH FAULT
Pressing ↓key repeatedly get
Main menu (represents Earth fault Time setting
has been set to 3.00sec), press → key (Submenu LED On) to get the Sub menu. Pressing
the ↑ or ↓ key, changes the time setting by 0.01sec increment or decrement. Upon
selecting the desired setting, once again press the → key (Sub menu LED goes OFF) to
return to the main menu.
6.3.2. LOW SET
a) For Inverse Characteristics
Pressing ↓ key repeatedly get
Main menu (represents Low set Time Multiplier
setting has been set to 1.000), press → key (Submenu LED On) to get the Sub menu.
Pressing the ↑ or ↓ key, changes the time setting by 0.025 increment or decrement. Upon
selecting the desired setting, once again press the → key (Sub menu LED goes OFF) to
return to the main menu.
b) For Definite Time Lag Characteristics
Pressing ↓ key repeatedly get
main menu (represents Low set Time setting has
been set to 3.00 sec), press → key (Submenu LED On) to get the Sub menu. Pressing the
↑ or ↓ key, changes the time setting by 0.01sec increment or decrement. Upon selecting
the desired setting, once again press the → key (Sub menu LED goes OFF) to return to the
main menu.
6.3.3. RESET TIME
Setting range: 0 sec to 60 sec in steps of 1 sec.
(Reset time is common for both Earth fault and Low set)
Pressing ↓key repeatedly get
Main menu (represents reset time has been chosen
as 0 sec). Press → key (Submenu LED On) to get Submenu. Pressing the ↑ or ↓ key,
16
changes reset time delay by 1 sec for each pressing. After selecting the desired setting,
once again press the → key (Sub menu LED goes OFF) to get back the main menu.
The recommended setting is 0sec.
6.4. Acceptance of Settings (ENTER)
For the relay to accept the above setting changes press X key once, now the display goes
off and the settings are updated. By pressing any key again
Indication will appear
Ensure all the chosen settings. In case of any changes required use Sub menu key and then
do the changes and finally press enter X key once.
ENSURE TO PRESS ‘ X ’ KEY TO ACCEPT THE CHANGES
7. TO CHECK THE RELAY VERSION
Press × key four times, example of relay version display is as follows:
- Represent MIT 161 relay version 1
To get back the main menu, press ↑ or ↓ key.
8. TO CANCEL SETTING WHILE CHANGING (CANCEL)
While the particular setting is being changed (using ↑ or ↓ key) with Submenu LED ON
by pressing X key, the original setting is restored
9. TRIP INDICATION AND RESETTING OF TRIP INDICATION (RESET)
When the relay operates, RED " TRIP" LED indicates tripping.
By pressing repeatedly the arrow key you will get all trip indication. That is if Earth fault
will reappear. Where as if both (Earth fault & Low set) are tripped
tripped
will appear alternatively for each pressing of the key.
Suppose Earth fault has started but not initiated trip, but Low set is tripped then pressing
any arrow key
(Indicates Earth fault is started)
(Indicates Low set is
operated) will appear alternatively for each pressing of the key.
Once the fault is cleared, press × key twice to reset the trip indication.
The trip indication and settings will be retained in Non - volatile memory during auxiliary
DC power supply failure.
17
COMMISSIONING
1. REQUIRED TEST EQUIPMENTS
•
•
•
•
•
500V insulation test sets.
Variable secondary injection current source rated 10A or greater.
Time interval meter
Primary injection equipment
A DC supply with a nominal voltage within the working range of the relays DC
auxiliary supply ratings
2. INSPECTION
Ensure that all connections are tight and in accordance with the relay wiring diagram and
the scheme diagram. Check if the relay is correctly programmed and the relay is fully
inserted into the case.
3. APPLYING SETTINGS
The relay settings for the particular application should be applied before any secondary
testing is started.
4. PRECAUTIONS
Before testing commences, the equipment should be isolated from the current
transformers and the CTs to be short-circuited, in line with the local site procedures. The
tripping and alarm circuits should also be isolated, where practical. Also, ensure that trip
links are removed.
Ensure that correct DC auxiliary voltage and polarity is applied. See the relevant scheme
diagrams for the relay connections.
5. TESTS
5.1. Insulation
Connect together all relay CT terminals and measure the insulation resistance between
these terminals and all the other relay terminals connected together to earth.
Connect together the terminals of the DC auxiliary supply (only +ve and -ve) and measure
the insulation resistance between these terminals and all other terminals connected
together to earth.
18
Connect together all the output relay terminals and measure the insulation resistance
between these terminals and all other terminals connected together to earth.
A minimum value of 2. 5 to 3 meg ohms can be considered as satisfactory value.
5.2. Secondary injection
Select the relay configuration and settings for the application. Note that the MIT relay can
be connected either as 1A or 5A-rated device. The user should check this before
commencing secondary test. Please refer Sec. 2.1. in installation
5.2.1. PICK UP AND RESET
The test checks accuracy of the current settings for the relay earth fault characteristics.
Apply single-phase current into the current inputs. Slowly increase the current until the
starter LED (yellow) operates and record the pick up current in Table 1. Reduce the
current until the LED goes off and record this as the reset level. Repeat this test for low set
also.
Check that all the pick up current levels are measured within 104% ± 4% of the applied
setting. Check that the reset levels are ≥ 94% of the setting.
POLE
PICK-UP
SETTING
MEASURED
PICK-UP
PICK-UP MEASURED
ERROR
RESET
RESET
ERROR
E/F
LOW SET
TABLE 1
5.2.2. IDMTL / DTL CHARACTERISTICS
This test checks the accuracy of the main time delay characteristics (IDMTL / DTL).
Select the relay current setting characteristics and time multiplier settings as required and
then inject a level of current which is a multiple of the relay setting.
A time interval meter should be connected to the correct output contact terminals. The
timer should be started by the source “ON" switch and stopped by the relay trip contacts.
Lowset should be selected. A secondary injection timing test circuit is illustrated in Fig. 6.
The secondary injection test equipment should be made 'OFF', once the relay contact is
closed.
19
Table 2 shows theoretical value of each characteristic with time multiplier set to 1.000.
Record the actual results in Table 3 and check that the measured times are within ± 5% or
± 30-m.secs.of theoretical value.
CURVE
2 x Is
5 x Is
10 x Is
20 x Is
SI 3
10.03
4.28
2.97
2.27
SI 1
4.39
1.87
1.3
1.0
EI
26.67
3.33
0.81
0.20
VI
13.50
3.38
1.50
0.71
LTI
120.00
30.0
13.33
6.32
DTL
*
*
TABLE 2
Pole
Characteristic 2 x Is
(SI3,SI1,EI,
Delay
VI LTI,DTL)
*
*
* USER SETTING
Error
(±5%)
5 x Is
Delay
Error
(±5%)
10 x Is
Delay Error
(±5%)
20 x Is
Delay
LOWSET
TABLE 3
5.2.3. OUTPUT CONTACTS COMBINATION
a) Starter - C/O
This contact is to be used while testing the pick up and reset value of the relay.
b) Common Trip & Alarm for E/F and LOW SET – 2 N/O contacts
These contacts to be used while testing the E/F & LOWSET characteristics.
c) E/F – 1 N/O contact
This contact to be used while testing the E/F characteristic.
20
Error
(±5%)
d) LOWSET - 1 N/O contact
This contact to be used while testing the LOWSET characteristic.
e) PROTECTION HEALTHY - 1 N/C contact
This contact indicates the relay healthiness.
5.3. Primary Injection
Primary injection tests are essential to check the ratio and polarity of the transformers as
well as the secondary wiring.
Ensure the instrument transformer is potential type and isolated from the primary system.
Using the circuit shown in Fig.7, check the current transformer ratio and CT phase to earth
connection. Inject a current of sufficient magnitude .The secondary current is
Is = Primary current / CT ratio
5.4. Putting Into Service
After completing all tests satisfactorily, the relay should be put into service as follows:
Make a final check of the secondary wiring and tightness of all terminal connections.
Insert the DC supply fuse.
Check the relay healthy indication/display.
Replace the relay cover.
Insert the trip links.
Perform trip test by secondary injection.
Remove all test connections
21
Double Pole switch *
240 V
A.C
SUPPLY
A
E/F
11
12
START
TIME
INTERVAL
METER
23
+ve
D.C SUPPLY
22
24
STOP
3
* Use good quality switch
Fig 6 - Secondary injection timing test circuit
(Terminals shown are for 1A rating)
22
4
-ve
MIT 161
I
E/F
A
11
12
I
+ve
D.C SUPPLY
22
24
23
PRIMARY INJECTION
TEST SOURCE
Fig 7 - Primary Injection Test Circuit for E/F Relay
(Terminals shown are for 1A rating)
23
-ve
24
R
EARTH
AUXILIARY
SUPPLY
Y
B
20
23
STARTER
PROTECTION
HEALTHY
LOWSET
EARTH
FAULT
TRIP
ALARM
11
9
8
17
16
7
6
5
4
CT SHORTING CONTACT
19
18
3
15
CASE TERMINALS VIEWED FROM REAR
10
21
20
2
14
1
13
1 1 A
wire and connect
1 1B
wire to
to Earthbar.
2. Terminal No.23 (Earth) is to be connected directly
fixed to a parking rack provided in the terminal block.
terminal number 11. Unused current terminal is tightly
For 5A tap remove
1. CT Circuit is shown connected to Relay 1A tap.
Note :
12
23
MIT161 - WIRING DIAGRAM
19
21
18
24
- VE
17
16
15
14
13
22
Earth Fault
4
3
2
1
+ VE
12
11B
11 1 1 A
MIT 161
22
24
Earth
(+) Ve
(-)Ve