CHAPTER 4
DISTANCE RELAY QUADRAMHO.
4.1) INTRODUCTION (MAIN FEATURES)
- It is a completely non switched relay and so the function of the starter is
eliminated. Each type of fault has its own measuring unit, therefore it has total of
18 MU’s. That means there will be 18 replica impedances etc. It is thus highly
reliable and fast.
- Suitable for single pole, three pole trippings.
- As it is non-switched, so it is much faster than other relays for 132Kv system.
Typical timings are 35 m sec for the first step. And fast operating time is
maintained for wide range of fault conditions.
- Used for medium and high voltage lines like 110 Kv and 132 Kv.
- It is using mho characteristic and is a partially cross polarized relay.
Quadrilaterals are also available.
- Since this relay is a product of GEC (now AREVA) therefore star point of Ct
will be towards line.
- Burden of the relay on Ct and Pt circuit is very low.
- It is a three zone relay. With an additional zone 3 reverse (Z’).
- Has additional features of PT fail, SOTF, Power swing blocking and all distance
relay schemes can be used one at a time. ( all these terms have been clarified in
the chapter for schemes.
- Minimum operating current is 20 % of I n.
4.2) SETTING CALCULATIONS
Consider the following 132 Kv system, with the relay at A “looking” towards B.
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The data for the above system is as below.
Pt ratio = 132Kv/ 110 V
Ct ratio= 600/5
Conductor= Zigolo/ lynx Z+ = 0.689 750
K0 = 0.65
Zone 1 = 85% of the first section i.e. AB
Z 1 Primary= 0.85 x 50 x 0.689 750
Z 1 Primary= 29.28 750 ohms
Z 2 Primary= AB complete + 50 % of 15 km line.
Z 2 Primary= 50 x 0.689 + 0.5 x 15 x 0.689
Z 2 Primary= 39.62 750 ohms
Z 3 Primary = AB complete + 50 % of BC.
Very important to note that in zone 2, zone 3 and in zone 4, flexibility is allowed in settings.
Z 3 Primary= 50 x 0.689 + 0.5 x 30 x 0.689
Z 3 Primary = 44.79 750 ohms
There is no Zone 4.
Secondary values
UZ = (Pt ratio) / (Ct ratio) = (132000 / 110) / (600/5) = 10
Z1 secondary = Z1 Primary / U Z = 29.28 / 10 = 2.928 750 ohms
Z2 secondary = Z2 Primary / U Z = 39.62 / 10 = 3.962 750 ohms
Z3 secondary = Z3 Primary / U Z = 44.79 / 10 = 4.479 750 ohms
Formula for the implementation of these values is such that we have coarse setting and fine setting.
Coarse setting once set will be common to all zones while fine setting is applied independently to each zone.
They are as under:
Z ph = (K1 + K2) / In K1 = 0- 4 (in steps of 1)
K2 = 0- 0.8 (in steps of 0.2)
We know that In is 5A. Now we will select the two in such a way that we get maximum value for Z ph but at
the same time, taking care, that zone 1 secondary is not in decimal points
When these limits are considered then we can safely have
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K1 = 4 and K2= 0.8
Z ph= (4+ 0.8)/ 5 = 0.96 ohms/ phase.
These settings are carried on the first module.
Other settings that are to be carried out on this module are :
K0 = (Z L0-Z L1)/ (3ZL1) = ZN / Z ph
Z N = K0 x Z ph = 0.65 x 0.96 =0.624
ZN is implemented with the help of the following formula:
ZN = (K4 + K5 + K6) / I n
Where K3 if fitted = 8, 16, 32, 40, 48.
K4 = 0 - 5 (in steps of 1)
K5 = 0 – 0.9 (in steps of 0.1)
K6 = 0 – 0.08 (in steps of 0.02)
Thus: Z N x I n= (K3 + K4 + K5) = 0.624 x 5= 3.12
K 4 = 3, K5 = 0.1 and K6 = 0.02
Zone settings are now calculated as under.
Z1= (K11 + K12 + K13) K14 x Z ph
Using the values of Z1 and Z ph
Z 1 / Z ph = (K11 + K12 + K13) K14
2.93 / 0.96 = 3.052
K11 = 1 to 9 (in steps of 1)
K12 = 0 t0 0.9 (Steps of 0.1)
K13 = 0 to 0.8 (steps of 0.02)
K14 = 1 and 5
Keeping in view the available values we get
K11 = 3 K12 = 0 K13= 0.06 (as we don’t have 0.05 we select one step higher or lower)
K14 = 1
Z2 = (K21 + K22) K14 x Z ph
Z 2 / Z ph = (K21 + K22) K14
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3.96 / 0.96 = 4.125
K21 = 1 to 9 (in steps of 1)
K22 = 0 t0 0.9 (Steps of 0.1)
K14 = Already set at 1
Keeping in view the available values we get
K21 = 4 K22 = 0.1 K14 = is already 1
Z3 = (K31 + K32) K33 x Z ph
Z 3 / Z ph = (K31 + K32) K33
4.48 / 0.96 = 4.66
K31 = 1 to 9 (in steps of 1)
K32 = 0 t0 0.9 (Steps of 0.1)
K33 = 1 or 5
Keeping in view the available values we get
K31 = 4 K32 = 0.7 K33 = 1 (first set this one)
Z3 = (K31 + K32) K33 x Z ph
Z 3 / Z ph = (K31 + K32) K33
4.48 / 0.96 = 4.66
K31 = 1 to 9 (in steps of 1)
K32 = 0 t0 0.9 (Steps of 0.1)
K33 = 1 or 5
Keeping in view the available values we get
K31 = 4 K32 = 0.7 K33 = 1 (first set this one)
Z3 ‘= 25 % of zone 1 reach
So, Z 3 ‘= 0.25 x 2.93= 0.73
The formula for Z3 ‘ is
Z 3’ = (K35 + K36) K33 x K 37 x Z ph
Z 3 ‘/ Z ph = (K35 + K36) K33 x K 37
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0.73 / 0.96 = 0.76
K35 = 1 to 9 (in steps of 1)
K36 = 0 t0 0.9 (Steps of 0.1)
K33 = 1 Already set.
K 37= 0.25, 0.5, 1.0
The infinity positions for K11, K15, and K21 are used for on load directional checks.
Keeping in view the available values we get
K35 = 1 K36 = 0.5 K33 = 1 (first set this one) and K37= 0.5
At this stage zone settings are completed and next we will set angle. (This will be setting the angle on replica
impedance M and in this relay angle for phase to phase faults and phase to ground faults are given separately).
Ø – Ø, Ø = 750
Ø – G, Ø = 700
This means that the mho circle for phase to ground will be slightly shifted towards the R axis. This
helps in giving better coverage for arcing faults. And since arcs in phase to ground are of greater resistance so
we shift to give compensation.
Timings for zones are such that zone time is inherent and that of zone 2 and zone 3 are set on
switches.
Schemes will be selected by using OPTION SELECT digits. This includes selection of single and
three pole tripping.
For detection of power swing two circles of the same shape as zone 3, are used. Although details are
in the chapter of schemes but here a brief idea is given – that the circles are called zone 5 and zone 6- that
these have no settings rather are automatically set by the relay itself by setting zone 5 = zone 3 and zone 6 at
120 % of zone 3.
Testing is made very easy by use of test plugs GEC make for these relays. ZFB test set, omicron and
even freja can be used for testing of these relays.
CHAPTER 5
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DISTANCE RELAY PYTS
5.1) INTRODUCTION (MAIN FEATURES)
The main features of this relay are:-
- Mho characteristic, fully cross polarized, switched relay- so maximum accuracy
in arcing faults.
- As static circuits are used, so they have low burden on Ct’s and Pt’s.
- K 0 compensation available.
- RCA (relay characteristic angle) from 30 to 850 available.
- Three directional zones Z 1, Z 2, Z 3 and the fourth zone is starter, which is non
directional but option is available to make it directional too.
- Two types of starters are available
i) under impedance starters and
ii) Over-current starters.
- Single and three phase tripping available.
- SOTF, PSB, and distance relay schemes can be used.
- Minimum operating current required is 25 % of I n.
5.2) SETTING CALCULATIONS
Consider the following system
Conductor: Zigolo/ lynx Z = 0.689 750 ohms/ km
Pt ratio: 132 Kv/ 110 V
Ct ratio: 600/5
K0: 0.7
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Zone 1 = 85% of the first section i.e. AB
Z 1 Primary= 0.85 x 50 x 0.689 750
Z 1 Primary= 29.2 750 ohms
Z 2 Primary= AB complete + 50 % of BC
Z 2 Primary= 50 x 0.689 + 0.5 x 30 x 0.689
Z 2 Primary= 44.78 750 ohms
Z 3 Primary = AB complete + BC complete + 50 % of CD.
Very important to note that in zone 2, zone 3 and in zone 4, flexibility is allowed in settings.
Z 3 Primary= 50 x 0.689 + 30 x 0.689 + 0.5 x 45 x 0.689
Z 3 Primary = 70.64 750 ohms
Next Zone 4
Z 4 Primary = 110 % of Z 3
Z4 Primary = 1.1 x 70.64 = 77 ohms. (Angle does not apply as it is direction less)
Secondary values
UZ = (Pt ratio) / (Ct ratio) = (132000 / 110) / (600/5) = 10
Z1 secondary = Z1 Primary / U Z = 29.2 / 10 = 2.92 750 ohms
Z2 secondary = Z2 Primary / U Z = 44.78 / 10 = 4.478 750 ohms
Z3 secondary = Z3 Primary / U Z = 70.64 / 10 = 7.064 750 ohms
Z4 secondary = Z4 Primary / U Z = 77 / 10 = 7.7 ohms (angle does not apply)
Formula for the implementation of these values is as under:
Z1 = K1 x K Z x K D
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K1 = 0.25, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 (in some it has a
continuous adjustment).
KZ = has tapings of 0,1,2,3,5,10,20 ohms for 1 A
relay and 0,0.2,0.4,0.6,1.0,2.0 and 4.0 for 5 A relay.
KD = Are range multipliers and are
0.1x,1 x,2 x, and ¥.
Z2 = K2 x K1x KZ x KD or Z2 = K 2 x Z1
K2 = 1, 1.2, 1.5, 2, 3, 4, 5, 10
Z3 = K3 x K1x KZ x KD or Z3 = K 3 x Z1
First we will set zone 1 such that
KZ x KD >= Z1
Hence we must have
KZ x KD >= 2.92
By checking the values for both K ‘s in above we see that we will have
KZ = 3 (it may not be available in some relays- they will have 4-so we will take 4)
and KD = 1
Thus 3 x 1>= 2.92
Or K1 x 3 x 1 = 2.92
K1 = 2.92 / 3 = 0.97
So zone 1 settings are KZ = 3, KD = 1 and K1 = 0.97
Zone 2 settings are
Z2 = K 2 x Z1
4.478 = K 2 x 2.92
K2 = 4.478 / 2.92 = 1.53
Zone 3 settings are
Z3 = K 3 x Z1
7.064 = K 3 x 2.92
K3 = 7.064 / 2.92 = 2.41.
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Zone 4 settings are
Z= K/ I
7.7 = K/ 5
7.7 * 5 = K
38.5 = K
All these settings of knobs on the relay will be set to achieve the desired settings. It is very important to note
that if a setting can not be implemented on a knob it is better to take the next higher so that the protection
zone is extended but care must be taken in zone 1, such that after extension zone 1 reach does not extend
beyond 90 % of the first section.
Other settings that are to be carried out are of K0 :
(Z L0-Z L1)/ (3ZL1) x Zone 1 settings = K1N x K ZN
K 0 x Zone 1 settings = K1N x K ZN
0.7 x 2.92 = 2.04
Therefore, select K1N and K ZN such that we get this value, and
K1N = 0.5 to 1.5 and
K ZN =
5.3) ADDITIONAL SETTINGS ON PYTS
:- module nos. 3
Link position A = Impedance starter.
B = When C.V.T is used with schemes
C = Over current starter.
:- module nos. 5
Link 2 – to make Z 4 directional or non directional
Link 6 – Blocking/ un-blocking starter tripping.
:- module nos. 6
Link 1 – Blocking/ un-blocking SOTF
Link 2 – Monitors SOTF through voltage and starters.
In PYTS relays there is another module for power swing settings. Although details of power swing
are to be explained in coming chapters but for the time being the settings are detailed below.
The outer reach of power swing circle is set on the left most module, while the inner circle will be that of Z 4.
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