The reverse busbar protection is a cost-effective solution for the accelerated clearance of busbar faults in distribution systems. It can only be applied on single busbars with a fixed direction of power flow and fault current flow. In picture 3, a typical application is shown.
review: For this application, the protection device on the incoming bay (usually the transformer bay) will be provided with blocking signals from the outgoing bays (the feeder bays). If one of the outgoing bays (feeder bays) detects a fault, (pick-up signal), this bay must route a blocking signal to protect the incoming bay. This blocking signal prevents the fast tripping of the incoming bay (I>> stage). The block signal may only be present for one second. For this application, a CFC chart in the incoming bay is required. Although it is possible to allocate a signal from a binary input so that it provides the blocking of a protection stage it is not possible to give more than one binary input to directly block one protection stage (the reason being that if two binary inputs that provide the same blocking signal have a different state, the device logic would not know which of the two binary inputs should be used).
Example application with 7SJ6 relays: The I>> stage in the in-comer will be blocked with the signal 1721 >Block 50-2., and the signal 1724 >Block 50N-2. These signals must be allocated with source CFC. (see picture 1)
Picture 1: input/output matrix in the incoming bay relay
For example, a feeder relay (or many feeder relays with a blocking signal connected in parallel) designated as LHBB-block provides a blocking input signal via binary input to the incoming bay relay. This signal is routed to the user-defined single-point annunciation in the matrix (picture 1), binary input 20. Similarly, the second feeder relay (or second group of relays) designated as RHBB-block is/are allocated to binary input 21. Two new user-defined single-point annunciations, which have to be connected to the binary inputs must be generated. These signals (in picture 1) are called LHBB-Block and RHBBBlock. These signals must be routed with the destination CFC so that they will be available inside the CFC charts. In the CFC chart, the LHBB-Block and RHBB-Block signals are connected via OR-gate. The output of the OR gate triggers a timer that restricts the blocking signal to one second. This is achieved by applying the timer output via a negator to an AND gate (AND gate 4 in picture 2). The timer output will change from 0 to 1 one second after the OR gate output changes to 1.
At this point, the second input of AND gate 4 will change to 0, thereby removing the blocking signal routed from OR gate one via the AND gate to the right-hand margin. As shown in picture 2, the blocking signal from the CFC chart is derived from the AND gate output and is routed to the signals 1721 >Block 50-2. and 1724 >Block 50N-2. Please note that the gates must be executed in the correct sequence, i.e. sequences 10 to 13 as shown in picture 2. The sequence of execution may commence with a different number, depending on other logic located in the same execution layer, PLC_BEARB). The OR gates must be first in the sequence, followed by the timer, negator, and AND gate in turn.
Picture 2: CFC chart to implement the blocking in the incoming bay
1. feeder: Protection device closest to fault release trip signal, & issues back signal to incoming bay 2. Fault on busbar: protection device in incoming bay issues fast trip with |>> stage after 50ms. None of the feeder bays pick up & therefore they do not issue a block signal.
This technical report refers to the electrical protection of all 132kV switchgear. These settings may be reevaluated during the commissioning, according to actual and measured values. Protection selectivity is partly considered in this report and could be also re-evaluated. Names of parameters in this calculation may differ from those in the appropriate device.
Technical Data of the Lines
Main Line
Conductor Type
ACSR Lynx
Length
27.8 km
Type
ZM Type Tower
Positive sequence impedance
0.1583 + j0.4004 (0.431 ∠68.4°) Ω/ km
Zero sequence impedance
0.3246 + j1.228 (1.27 ∠75.2°) Ω/ km
Current capacity (A)
487
Next Line
Conductor Type
ACSR Lynx
Length
36 km
Type
ZM Type Tower
Positive sequence impedance
0.1583 + j0.4004 (0.431 ∠68.4°) Ω/ km
Zero sequence impedance
0.3246 + j1.228 (1.27 ∠75.2°) Ω/ km
Current capacity (A)
487
SEL 311 – Line Protection
Protection Settings Calculations for Lines
SEL-311C Distance Protection Settings Distance Zone Non-Homogeneous Correction Angle Load Impedance and Load Encroachment Power Swing Detection/ Out of Step Detection Switch on to Fault (SOTF) Fuse failure scheme OR Loss of Potential (LOP) SEL-351A Back-up Over Current Settings Back up over current settings
Technical Data of the Power Transformers
Transformers-1
Type of cooling
ONAN / ONAF
Vector Group
Dyn11
Rated Voltage HV V
132000
Rated Voltage LV (V)
11500
Full Load current HV ( A)
87.48 / 113.72
Full Load current LV (A)
1004.12 / 1305.35
Rated Power ( MVA)
20 / 26
% impedance at the normal tap (12 no.)
10.15% / 13.20 %
Type of tap changer
On load
the voltage at the maximum tap (V)
145200
The voltage at the minimum tap (V)
118800
Transformers- 2
Type of cooling
ONAN / ONAF
Vector Group
Dyn11
Rated Voltage HV (V)
132000
Rated Voltage LV (V)
11500
Full Load current HV ( A)
43.7 / 56.9
Full Load current LV (A)
502 / 652.7
Rated Power ( MVA)
10 / 13
% impedance at the normal tap (12 no.)
10.15% / 13.20 %
Type of tap changer
On load
The voltage at the maximum tap (V)
145200
The voltage at the minimum tap (V)
118800
SEL-787 Transformer Protection Relay
Protection Settings Calculations for Power Transformers
2. now we will export selected (Binary inputs/ Binary outputs/ Analog inputs/ goose receive) to excel
3. collapse all rows/ columns and expand all rows/ columns
4. General filter and particular row/ column filter
5. You can change the user-defined for particular selected inputs/output of type binary/analog by clicking on properties and changing the name.
6. Map some goose receive signals by double click, create a connection between selected columns and rows.
7. Double click on the existing connection will disconnect the existing connection between the selected column and row.
8. Some redo and undo.
9. Try to find some signal using find. Find will Highlight the signal where it is.
10. Double click on a particular group of items in any rows or columns to hide or show.
11. Create an inverted signal in Binary outputs/inputs
12. You can see a Glue logic inverter created because of mapping “I” in the signal matrix.
13. flip column text to horizontal/ vertical for binary inputs/ binary outputs/analog inputs/goose receive
These pictures are part of our supplementary files for ABB PCM 600 training that is mixed with Oral explanations to help you understand this course. These auxiliary files have been gathered and attached to our ABB PCM600 training course, you can get more information by
To migrate the IED version, Right-click on IED & select Migrate Configuration. IED Version Initial before MIgration: 1.2.3
Let us migrate the IED version to 1.1.01
3. Click Continue to migrate. Undo is not possible in between or end of the migration. The old configuration will be backed up in the path…\PCMDataBases|PCMBackup
4. migration details will popup showing what are the changes that will be made in the migration process like function or hardware version/reversion changes or removed or not available.
5. click Next to proceed further
6. Migration process started, Progress bar showing the details, what are the steps taken in the migration process is also shown.
7. Shoe IED Configuration migration report is selected by default. Click Finish now.
8. Migration report will tell u, Worksheet Name, Type, Name, and what happened during migration u can save this report by clicking on the save icon for further reference.
9. open the Migration Report which is saved as a PDF
These pictures are part of our supplementary files for ABB PCM 600 training that is mix with Oral explanations to help you in the best way of understanding this course. These auxiliary files have been gathered and attached to our ABB PCM600 training course, you can get more information by
Transformers and Generators are classified as voltage sources. They are mainly, protected by an overcurrent + earth fault relay usually installed in the breaker panel. It should be noted that this protection is not enough alone.
When an earth fault occurs within the A zone in the following figure (Internal fault), or within the machine, the fault current will circulate within the zone or the machine. The fault current will not flow through the CTs connected to the O/C +E/F relays near the breaker. This will cause a no-trip situation when there is a fault in zone A.
Overcurrent + Earth fault relay
Consequently, to detect internal earth faults a separate scheme is necessary. This scheme is called Restricted Earth Fault (REF). It should be noted that the fault currents in Zone A are limited by the impedance of the equipment in the zone – for transformers and generators it is very low – the fault currents can rise very fast and damage the equipment. So, REF protection is of utmost importance for generators and transformers.
Reason to call it Restricted E/F?
The Restricted name is derived since the objective of the protection is to detect the earth fault restricted to the specific zone, and it’s starting from the breaker to the machine terminals. In the case of a generator, the machine terminal is the neutral point. In the case of a transformer, the machine terminal becomes the star point of either the primary or secondary winding or both. In the case of delta winding, it is the winding itself.
Way to detect internal earth faults?
It is well established that the sum of currents at the beginning of zone A should be equal to the sum of currents exiting the zone. Two sets of CTs are used to derive the sum of currents at the inlet and exit. A fault in the zone will result in a difference in current.
An overcurrent relay is for measuring the difference in the sum of these currents. Fig. 2 shows a typical REF scheme is shown. The REF relay is connected between P & S. It will pick up if there is enough voltage across P-S to drive the pickup current through the relay.
Principle of Restricted Earth fault Protection
There are two current sources in the CT secondary circuit PQRSTU:
the current produced by CT X (loop RSPQ)
the current produced by CT Y (loop UPST)
A vectorial sum of the currents for these two CTs will be equal and opposite in the branch P-S (ie), and the resultant current in the branch PS will be zero under normal conditions. In this situation, the currents of CT X and CT Y will circulate in the loop PQRSTU. The voltage across P-S will be zero.
In case that an earth fault within zone A, the currents of X & Y CTs will not be equal, small difference in current will flow in the branch P-S. This current will result in a voltage across P-S – since the current flows through the relay impedance. If this voltage is suited to operate the relay, the relay will pick up – thus detecting a fault within the zone.
What if a fault occurs outside the zone?
For a fault outside the zone, the currents through CTs X & Y will be the same the resultant current through P-S will still be zero and the relay will not pick up. In this case, the fault has to be cleared by another O/C + E/F relay connected near the breaker.
The reason for needing a Stabilizing resistor required in the REF scheme?
It is mentioned in sections 3 & 4 that the REF relay will detect a fault within a zone restricted between two CTs and it will not detect a fault outside the zone defined by the CTs. This is true, only for ideal conditions- where the two CTs are entirely matched. Following mismatches will occur under practical situations in the field:
the CT secondary impedances may not be equal
the lead wires connecting the CT secondaries to the relay may not have equal resistance
the CTs may have different ratio errors and phase angle errors – due to this, the secondary currents will not be equal even if the primary currents are the same
the CTs may have different saturation characteristics – this will cause a small difference in the secondary currents for the same primary current
The cumulative effect of all the above can make the relay trip even when there is a full load current flowing in the primaries – through the primary side currents are the same, the secondary side currents need not be the same – a voltage sufficient to trip the REF relay may develop across P-S and hence the relay will trip.
To make the relay insensitive to this voltage produced by CT mismatch, a resistor is added in series with the relay. Once this resistor is added, the relay will need a voltage that is higher than the voltage produced by the CT mismatch. This resistor is called a stabilizing resistor – this is an important component in the REF scheme –since this ensures stability in the scheme by avoiding spurious tripping.
knee point voltage
It should be noted that the actual input circuit to the trip mechanism (consisting of the relay + stabilizing resistor) has become a high impedance circuit. If the relay has to trip, the CT secondaries should produce sufficiently high enough voltage to activate the relay, after allowing for the drop across the stabilizing resistor.
To ensure the CTs produce enough voltage, an additional specification the Knee point voltage – is included for the CTs used for REF protection.
Knee point voltage (KPV)is defined as the point on the magnetizing curve (of the material used for the CT core) where the core will need a 50% increase in the magnetizing force (ampere-turns) to cause a 10% increase in the flux density. (voltage build-up across secondary). In effect, KPV defines the end of the linear portion of the BH curve. The higher the KPV, the larger the linear zone and the better will be secondary output for higher fault currents. The higher the KPV, the better the chances of a high-impedance relay trip.
Way of calculating the value of the stabilizing resistor and KPV?
The value of the stabilizing resistor and KPV will depend on the following parameters which are unique to a given feeder:
The impedance of the CT secondaries
Lead wire resistance between the CT secondaries and the REF relay
The impedance of the REF relay – this can vary concerning pick upsetting. We have to consider the relay impedance at the pickup setting being contemplated for the feeder.
The maximum fault current which can occur on the CT secondary side CTmmmm should not saturate under these maximum fault conditions. If the CT saturates, it will offer an alternate path for the resultant current and the REF relay may not trip.
What are L&T solutions for REF protections?
L&T manufactures a high impedance Overcurrent relay which is ideally suited for the REF protection of generators and transformers. Typical schemes are shown in figure 3 and figure 4.
L&T offers a unique feature in the REF relay SC14S – in addition to the instantaneous trip, the user can select a definite time delay of either 100 milliseconds or 200 milliseconds. In the case of small transformers & generators ( up to 5 MVA), the feeder trips during breaker closing. This mainly is due to the large inrush current causing a momentary difference in CT secondary currents due to a mismatch in saturation characteristics. A 100-millisecond time delay will help in this case.
Figure 3 shows a typical scheme for REF protection for generators. The scheme envisages the following;
3 nos. phase CTs
1 no. neutral CT
1 no. Relay SC14S
1 no. Stabilizing resistor
The below figure shows a typical scheme for REF protection for transformers. It should be noted that transformers will need two REF schemes – one on the primary side and the other on the secondary side.
For the transformer’s primary side, which is usually delta connected, the following are envisaged in the REF scheme:
3 nos. phase CTs
1 no. Relay SC14S
1 no. Stabilizing resistor
For the transformer’s secondary side, which is usually star connected, the following are envisaged in the REF scheme:
3 nos. phase CTs
1 no. neutral CT
1 no. Relay SC14S
1 no. Stabilizing resistor
Restricted Earth fault Protection scheme for transformer
Check the appearance of the motor; Check for body damage or damage to the cooling fan blade or shaft
Manually rotate the shaft to check the bearing condition; Check for free & smooth rotation.
Note the motor data from the motor NAMEPLATE
Earth Continuity: Use your ohmmeter to verify the resistance between the earth and the motor frame is less than 0.5 Ω
Power supply– correct voltage (230 volts per line), 415 v between Ll to L2, L2 to L3, and, L3 to L1
Three-phase motor
Three Phase:
Ensure the terminal for the power supply is in good condition. Check the connection bar for the terminal (U, V, W ). Connection type – STAR OR DELTA
Confirm the power supply VOLTAGE for the electric motor. 230/400.
Using the multimeter, check the continuity of winding from phase to phase (U to V, V to W, W to U). Each phase to phase must have continuity if the winding is OK
Check the motor winding ohms reading using a multimeter or ohmmeter for the phase-to-phase terminal (U to V, V to W, W to U ). The ohms reading for each winding must be the same (or nearly the same)
Insulation resistance of motor winding using Insulation tester meter set to the 500 Volt scale (1000v DC). 1. Check from phase to phase (U to V, V to W, W to U) and 2. check from phase to earthing (U to E, V to E, W to E). The minimum test value of the electric motor is 1 Meg Ohm (1 MΩ)
With the motor running, check the running amps of the motor using a Clamp on the meter. Compare to the FLA on the nameplate of the motor.
If every step is completed, decide whether the condition of an electrical motor is either OK or NEED TO REPAIR
Single Phase
Check the motor winding ohms reading using a multimeter or ohmmeter. (C to S, C to R, S to R). The reading for starting to run should be equal to C to S + C to R.
single-phase motor
Correct electrical terminal identification
There are three-terminal connections on a hermetically sealed motor compressor which are as follows: Common (C), Start (S), and Run (R). To identify the correct terminal connection the following procedure applies:
The highest resistance reading is between the start and run terminals
The middle resistance reading is between the start and common terminals.
The lowest resistance reading is between the run and common terminals.
