EASUN REYROLLE LIMITED MIB202 User guide

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OCTOBER 2003
APPLICATION AND COMMISSIONING
MANUAL FOR NUMERICAL BIASED
DIFFERENTIAL PROTECTION RELAY
TYPE - MIB202
EASUN REYROLLE LIMITED

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ISSUE NO : 1st Issue
DATE OF ISSUE : 01 - 10 - 2003
DEPARTMENT :AS

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CONTENTS
PAGE
APPLICATION 4 - 9
INSTALLATION 10 - 19
COMMISSIONING 20- 25
DRAWING 26

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APPLICATION
The MIB202 is micro-controller based Numerical Biased Differential
Protection Relay with inbuild Current Amplitude and Vector Group
Compensation features and also with Instantaneous Differential Highset
Element for two winding Power Transformer and AutoTransformers.
MIB202 relay, which can be used to operate for internal faults, like
phase to phase, phase to earth and inter turn faults in the
Transformers.
The same relay, we can use for 1A or 5A CT input on both LV & HV side.
The relay has supervisory components and self-monitoring features give
high confidence of serviceability.
1.0 BIASED DIFFERENTIAL PROTECTION:
The currents entering and leaving the transformer are measured, taking
in to the Power Transformer vector grouping and transformation ratio.
Software interposing current transformers can be applied to each set of
current inputs to correct for any magnitude and vector mismatch and to
remove zero sequence components where necessary. They are then
summed to form an operate signal which is applied to a three part
biased differential characteristic on a phase by phase basis.
The relay is provided with triple slope characteristics.
1. Initial Differential setting
2. Differential Bias slope
3. Differential Bias slope limit
1.1 INITIAL DIFFERENTIAL SETTING:
This is the value of current, expressed as a percentage of the chosen
current rating, at which the relay will operate with zero bias current. Its
setting would normally be the same as that for the differential bias slope
value.
Setting Range:
I - 10% to 50% of In in steps of 5%

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1.2 DIFFERENTIAL BIAS SLOPE:
Some unbalance current will appear in the differential circuit of the relay
for predictable reasons, e.g. due to the transformer tap position and to
CT errors. The current will increase with increasing load or through fault
current in the transformer so, to maintain stability, the biasing current
must increase proportionately. The bias slope expresses the current to
operate the relay as a percentage of the biasing (restraint) current. The
differential bias slope setting chosen must be greater than the
maximum predictable percentage unbalance.
Setting Range:
bS - 10% to 70% of In in steps of 5%
1.3 DIFFERENTIAL BIAS SLOPE LIMIT:
This setting defines the upper limit of the bias slope and is expressed in
multiples of nominal rated current. A setting value must be chosen
which will cover the maximum through fault current of the transformer.
This setting gives more stability during CT saturation for heavy through
fault.
Setting Range:
SL - 200% to 2000% of In in steps of 100%
2.0 DIFFERENTIAL INSTANTANEOUS HIGHSET OVER
CURRENT:
This is an unbiased, instantaneous element in the differential circuit with
a range of settings expressed as percentages of the nominal current
rating. If the feature is not required, the OFF setting should be selected.
If it is required, it must be set to a value in excess of any predictable
differential current, i.e. the differential current under maximum through
fault conditions with the transformer tap changer in its extreme position
and the differential current due to magnetizing inrush. The highset
should be set as low as possible but not less than the maximum three
phase through fault current and not less than the maximum
magnetizing current.
Setting Range:
H - OFF, 400% to 2500% of In in steps of 100%

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3.0 MAGNETIZING INRUSH RESTRAINT:
Second Harmonic quantities are calculated from the signal I1 - I2 to
provide an inhibit signal to prevent the protection operating for
magnetizing inrush conditions. Magnetizing inrush on any phase will
inhibit all three phases.
4.0 INTERPOSING CT MULTIPLIER (HV AND LV SIDE):
This range of settings enable the effective ratio of the HV & LV CT's to
be adjusted.
Setting Range:
Ah & Al - 0.50 to 2.50 in steps of 0.01
5.0 HV INTERPOSING CT CONNECTION:
An equivalent interposing CT connection can be selected from this range
of settings. The settings define the LV and HV winding configuration.
E.g. Yd, followed by the angular position of the LV phasor with respect
to the HV phasor. The angular position is described by the hour - hand
position on the twelve-hour clock face, e.g. Yd1 or Yd11. In each
setting, this is followed by the same angular relationship expressed in
degrees. The complete Yd1 setting will therefore read Yd1, -30°and
Yd11 will read Yd11, 30°.
Setting Range:
Vh - Yy0, Yy2, Yy4, Yy6, Yy8, Yy10, Yd1, Yd3, Yd5, Yd7,
Yd9, Yd11, Ydy0 and Ydy6
6.0 LV INTERPOSING CT CONNECTION:
As the HV connection but now applied to the LV CT's.
Setting Range:
VL - Yy0, Yy2, Yy4, Yy6, Yy8, Yy10, Yd1, Yd3, Yd5, Yd7,
Yd9, Yd11, Ydy0 and Ydy6

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7.0 TYPICAL RELAY SETTING CALCULATION
Power Transformer Details:
Voltage = 132 / 33KV
Rating = 60MVA
Tap Changer = +5% - 15%
Vector Group = Yd1
Current Transformer Details:
CT Ratio
For HV Side = 300/1
For LV Side = 1200/1
Calculation:
HV rated current = 60MVA / (132 * 1.732)
= 262.4A.
CT ratio for HV side is 300/1
LV rated current = 60MVA / (33* 1.732)
= 1049.76A
CT ratio for LV side is 1200/1
Mean tap value = [(+5) + (-15)] / 2 = -5%
HV current at –5% tap = (60MVA) / (1.732 * 132KV *0.95)
= 276.2A
HV Multiplier = 300 / 276.2 = 1.086 = 1.09
LV CT secondary current = 1049.7 / 1200
= 0.87475A
So the LV multiplier = 1200 / 1049.7 = 1.143
= 1.14
Initial Setting = 200mA (20%) or
2 times of maximum spill current
whichever is greater.
Bias setting = 20%
2 times of maximum tap change %
Bias Slope Limit = 4 times of full load current
HV ICT vector connection = Yd1, 30
LV ICT vector connection = Yy0, 0
HV ICT multiplier = 1.09
LV ICT multiplier = 1.14

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8.0 INTERPOSING CT SELECTION GUIDE
Power Transformer Vector
Group
HV
Interposing
CT Selection
LV
Interposing
CT Selection
Yy0, YNy0, Yyn0, YNyn0, Ydy0,
Yndy0, Ydyn0, YNdyn0
Yd1,30° Yd1,30°
Yd1, YNd1 Yd1,30° Yy0,0°
Yd1, YNd1 + Earthing Transformer Yd1,30° Ydy0,0°
Yy2, YNy2, Yyn2, YNyn2, Ydy2,
Yndy2, Ydyn2, YNdyn2
Yd3,90° Yd1,30°
Yd3, YNd3 Yd3,90° Yy0,0°
Yd3, YNd3 + Earthing Transformer Yd3,90° Ydy0,0°
Yy4, YNy4, Yyn4, YNyn4, Ydy4,
Yndy4, Ydyn4, YNdyn4
Yd5,150° Yd1,30°
Yd5, YNd5 Yd5,150° Yy0,0°
Yd5, YNd5 + Earthing Transformer Yd5,150° Ydy0,0°
Yy6, YNy6, Yyn6, YNyn6, Ydy6,
Yndy6, Ydyn6, YNdyn6
Yd7,-150° Yd1,30°
Yd7, YNd7 Yd7,-150° Yy0,0°
Yd7, YNd7 + Earthing Transformer Yd7,-150° Ydy0,0°
Yy8, YNy8, Yyn8, YNyn8, Ydy8,
Yndy8, Ydyn8, YNdyn8
Yd9,-90° Yd1,30°
Yd9, YNd9 Yd9,-90° Yy0,0°
Yd9, YNd9 + Earthing Transformer Yd9,-90° Ydy0,0°
Yy10, YNy10, Yyn10, YNyn10, Ydy10,
Yndy10, Ydyn10, YNdyn10
Yd11,-30° Yd1,30°

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Yd11, YNd11 Yd11,-30° Yy0,0°
Yd11, YNd11 + Earthing Transformer Yd11,-30° Ydy0,0°
Dy1, Dyn1 Ydy0,0° Yd11,-30°
Dy1, Dyn1 + Earthing Transformer Ydy0,0° Yd11,-30°
Dy3, Dyn3 Ydy0,0° Yd9,-90°
Dy3, Dyn3 + Earthing Transformer Ydy0,0° Yd9,-90°
Dy5, Dyn5 Ydy0,0° Yd7,-150°
Dy5, Dyn5 + Earthing Transformer Ydy0,0° Yd7,-150°
Dy7, Dyn7 Ydy0,0° Yd5,150°
Dy7, Dyn7 + Earthing Transformer Ydy0,0° Yd5,150°
Dy9, Dyn9 Ydy0,0° Yd3,90°
Dy9, Dyn9 + Earthing Transformer Ydy0,0° Yd3,90°
Dy11, Dyn11 Ydy0,0° Yd1,30°
Dy11, Dyn11 + Earthing Transformer Ydy0,0° Yd1,30°
Notes:
1. Y or y denotes an unearthed star connection on the HV or LV side
of the transformer respectively.
2. YN or yn denotes an earthed star connection on the HV or LV side
of the transformer respectively.
3. D or d denotes a delta connection on the HV or LV side of the
transformer respectively.

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INSTALLATION
1.1 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.
1.2 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.
1.3 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.
1.4 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