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– Anyone knows why we are using this diode and what it uses
1). Normal Diode allows current to flow in forwarding bias.
2). Zenner Diode allows current to flow in reverse bias only.

-Two phases show negative values but one phase shows positive values, how?
– Depend on load, may you try to tracing 3 line diagram until load (wiring internal of load equipment). Depend on load, may you try to trace 3 line diagram until load (wiring internal of load equipment)
– If the vts at 3phases exposed to fault what is the overcurrent protection behavior on this circuit? If all the electrical protections failed at the substation and just the physical protection operate what is the problem with this substation?

1), how we can detect CT saturation in the case of Low Impedance Relays?
2). Why is it essential to detect CT saturation only in case of low impedance Relays?
– I need a proper to the point response (no white paper/presentation please) for my proper understanding of this CT saturation detection technique.

– Can anyone tell me about the 400kV Busbar protection type?
https://electrical-engineering-portal.com/busbar-protection-schemes

– What is the main Function of the CSD relay?
– Controlled switching device (either implemented using a point on wave device or pre-insertion resistors in circuit breakers) helps achieve switching at either voltage zero or current zero (depending on the equipment to be switched) for instance a capacitor bank you would switch at voltage zero whereas for an inductor you would switch at current zero. CSD is typically applied in long transmission lines, filter banks, or converter transformers. By using CSD in the above cases it helps to prevent switching overvoltages or high inrush currents in the transformers.
– Can I use it for Breaker controlling?
– Basically, that’s what it does it controls the breaker to close or open at a certain point on the current or voltage waveform.


– What is the main purpose of reactors in the Power grid?
– Used for Reactive power compensation and to reduce Ferrantic effect, Reduce THD. also means Total harmonic distortion. Maintains Stable voltage profile by reducing Ferranti effect

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– What is the purpose of node VT Inside GIS, It’s 500kV?
– In 400kV or above voltage in line bay PT is also used. So this node PT is considered as line PT

– Maybe he’s asking what is the function of Node VT in SLD installed.
– I believe this PT is used for high metering and protection purposes at 500kV. Yes function of node VT in 500 kV GIS. Protection and metering at line side income. please see also of another VT in here At each bay Line and ATR or is considering for differential protection?
– try to find the secondary wire
– I think this is right: Synch + OV Protection in EHV system As a voltage Synchron check

– How to calculate 1ph & 3ph pickup for T60 relay
– Better refer to T60 Manual. The formula was given to calculate 1ph and 3 ph pickup. Check GE website


– What is the difference between Earthing transformer and NGR?
– Earthing transformer is used to provide grounding to the ungrounded electrical system or delta-connected system.
Whereas NGR is a grounding system, which is used to limit Earth fault current at a certain value.
– Where it is used widely?
– It is used for Generators, motors. This means wherever rotating machines are there we can use NGR to limit the earth fault current for preventing stator core to get damage.
– NGR is a neutral grounding reactor. It is used to cancel the capacitive current during fault. It’s effective in single-phase fault when a fault occurs on one phase and capacitive current flows from normal phases. NRG causes reactive to neutralize the capacitive Current from healthy phases.

– Can anyone let me know how to monitor the I/O IN CFC online mode the actual values in CFC?
– Siemens relay
– which logic do you want to monitor?
– Any logic I want to monitor the actual IO values
– Same as in MICOM
– want to see the values in SIEMENS CFC logic
– Watch ON in Siemens software is not activated
– Resistor and reactor both different components, the reactor is basically used on long TX lines where single-phase tripping is allowed.
– For controlling fault current of very low magnitude, a resistor should be chosen. However, where you need to limit the fault current of the magnitude of thousands of amps, you must choose a quality power reactor.
– NGR is never a Neutral Grounding Reactor.
It is always a Neutral Grounding Resistor (NGR). NGR is installed to a) limit the earth fault current below the full load current of transformer/ Generator to protect its lamination
b). This earth fault current must be greater than the capacitive current in the system (generated through the Bus-ducts, cables ) so that Arcing fault doesn’t take place across the NGR.
– Resistance and Reactor are resistors.

– In my company having a 14.24MW generator. Generator rotor resistance is changing continuously from 20 to 60 Kohm. What would be the reason behind it?
– Because of this rotor earth fault stage 1 operated because the setting is about 25kohm
– We also measure the current in earthing cable which is connected to the rotor shaft with slipring
– Temperature also changing?
– Not measured
– Resistance related to isolation, isolation related to temperature


– I want to know how to configure AR Block in P841. I have assigned one output contact and it is continuously high.
– If you are assigning AR block output contact with AR block DDB then it will remain high as long as the AR func is enabled, Use your conditions in the OR gate for AR block output contact. Not the DDB
– The output is continuously high either the function is off or on!
– Yep I remember. It will remain high. As its, the DDB used for other purposes during AR function
– Use your blocking conditions in OR gate for Output contact, not this DDB
– Anyone can share the procedure of the bump test motor.

– In a one and a half breaker scheme, the current magnitude from Q1 CB is different from Q3 CB, Can anyone explain this reason? The line is terminating between Q1 and Q3 CB. Also, there is a neutral current of 40A flowing from these CBS
– alarm is on both governors
– You may be done to check Fuel Management of that Turbine
– That looks like using PID & Close loop control system
A governor is a system that is used to maintain the mean speed of an engine, within certain limits, under fluctuating load conditions. It does this by regulating and controlling the amount of fuel supplied to the engine. The governor hence limits the speed of the engine when it is running at the no-load condition, i.e it governs the idle speed, and ensures that the engine speed does not exceed the maximum value as specified by the manufacturers.

– All marine vessels need a speed control system to control and govern the speed of the propulsion plant being used onboard, as there can be a large number of variations that arise on engine load, which may damage the engine and cause loss of life and equipment. The variations in the load on the engine may arise due to several factors such as rough seas, rolling and pitching of the vessel, compromised ship structure, changes in weight of the ship among others. what could be the reason for fuel management?
– And usually for power generation (coupling to generator) also considering the internal turbine/engine/generator/auxiliary condition. All speed control systems
almost using logic gate Proportional Integral Derivative.
– Safety and performance reasons.
– An increase in the load decreases engine speed. In this case, the flyweights move inwards, and that the governor spindle moves downward under the action of the force of the speeder spring. This movement lowers the pilot control valve which directs oil to the underside of the power piston.
As the hydraulic pressure on the piston overcomes the spring force acting on it, the piston moves upward and fuel supply to the system engine is increased. hence increasing its speed. Once the RPM of the engine increases, the control valve rises back to its initial position that blocks the
delivery of hydraulic fluid to the power piston.
On the other hand, as the load on the engine is decreased and its speed increases, the outward movement of the flyweights under the action of the additional centrifugal force causes subsequent upward movement of the spindle and hence the pilot control valve rises as well. This opens the port such that the hydraulic oil in the system flows to the oil sump from under the power piston through a drainage passage. The power piston then moves downwards under the action of the spring force and reduced hydraulic pressure and hence reduces the amount of fuel supplied to the engine is decreased. This reduces the engine speed and consequently, the forces on the flyweights are balanced once again. When operating generator synchronized, speed control merged with load sharing control system.
-Internal and external parameters are being calculation to the desire of speed of the engine/turbine.
– An Electronic governor provides engine speed adjustment from no-load condition to full load. It consists of a Controller, an Electro-Magnetic Pickup (MPU), and an actuator (ACT) to carry out the necessary speed control and regulation. The MPU is a micro-generator and has a magnetic field. It consists of a permanent magnet with an external coil winding. As shown in the diagram, the MPU is installed above the flywheel teeth, and depending upon its distance from the gear teeth or slot, the magnetic field of the MPU varies from a maximum to minimum respectively.
Due to the constantly changing internal magnetic field, an AC voltage and frequency are generated in the outer conducting coil. This AC voltage follows the speed of the flywheel. This is the most important aspect of the electronic control system as the governor controller converts the obtained frequency into a DC voltage signal. It then compares this with a set voltage. The results are calculated by a PID control (Proportional-integral-differential) and finally, the output reaches the actuator which implements the required corrections on the fuel supply to the engine.

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– we have 2 generators running in parallel. Parallel operating should be using load-sharing control mode or speed droop control mode to desire speed control of the engine.
– Yes
– Anyway, What are the model of both turbines?
– You will see at the logic control real-time/configuration software. That mentions dead band value. Then that will answer your question.
– have you manual of this 505 governor?
– Almost all types of governors are fitted with a flyweight assembly. Two or Four flyweights are mounted on a rotating ball head that is driven directly by the engine shaft, using a gear drive assembly. The rotation of the ball heads creates a centrifugal force that acts on the flyweights of the assembly and causes them to move outward, away from their axis of rotation. As the speed of rotation is increased and the degree of outward movement of the flyweights also increases, and vice versa, and hence the movement of the flyweights depends on the engine speed.
A spring is installed to counteracts the centrifugal force generated on the flyweights and force them towards their initial position. This spring is known as the speeder spring. The position of the flyweights and their outward movement is transmitted to a spindle (this may be done through a collar), which is free to move in a reciprocating fashion. The movement of this spindle, which forms the control sleeve, actuates a linkage to the fuel pump control and ultimately controls the amount of fuel injected.
– Under normal operational circumstances, i.e. constant speed and loads, the control sleeve remains stationary as the force on the flyweights is balanced by the counteracting force exerted by the speeder spring.
As the load on the engine is increased, the speed of the engine reduces and the control sleeve moves downward, as the force exerted on it by the speeder spring overcomes the force exerted by the flyweights.
The downward movement of the sleeve is linked to the fuel control racks such that there is an increase the fuel delivery and thus the power generated by the engine. The force on the flyweights increases with the engine RPM and once again the system comes back to equilibrium.
As the load on the engine is decreased, its speed increases. The flyweights move outward and in turn, the control sleeve moves up as the centrifugal force overcomes the speeder spring force. The movement of the sleeve actuates the fuel pump, fuel delivery is lowered, thus the speed of the engine is reduced and the system comes into equilibrium.

– I’m exporting the icd file for GE’s L90 but the IED name seems to be exported as a template. Does anyone know the reason?
– These are the server configurations with the IED name.
– What are the Commissioning procedures of HV/EHV equipment and different types of tests required before and After Energising the new lines/feeders, Transformers/Reactors?
-I need help to analyze this Disturbance Fault Record whether it is due to Lighting or Flash
– It was fault on Line Diff and Reclose on Phase R

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– how to know the wave of the current and voltage whether it was short on an insulator or due to the lightning strike?
– SF6 is good? Contact Resistance of CB checked during commissioning?
– I think CB operates at the right time.
– I think is not about a simultaneous issue, but probably a contact point issue. This a disturbance record from a relay right?
– How can you say it is a lightning strike?
– We check it by climbing on the tower located from the Fault Locator relay.
– What is the full form STUB?
– Stub is the noun itself. No full form
– When the isolator is open, keeping CBS closed in one and a half, this whole arrangement is known as stub bus. Stub is in one and a half breaker scheme

– Micom p841 auto recloser does not save disturbance record. Can anyone state what could be the reason?
– You tried to extract from disturbance records Or Check whether the fault trigger is triggered by all BI & BO?
– When I try to extract from the relay, it shows no disturbance record found
– That means, please check your PSL file
– Nothing triggered
– Change duration, trigger position. Input 1 trigger, change to L/H
– I have the p443 relay installed and its DR is working fine and configured as shown below. Likewise, change all digital inputs as per your requirement, Then check your PSL file.
– Both P441 and P841 PSL, how fault trigger input assigned?

– Relay is switching off when connecting with the SELC662 cable. Any idea on this issue?
– The main reason that can cause switching off of an IED upon touching it is normally related to the power supply card. Can you check if there is not loose contact with the power supply?
– Rear connection is fine

– How to reset lockout alarm in auto recloser relay using FnKey?
– LEDs get reset through FnKey configuration but not lockout. I have to insert a password for resetting it.
– Check your binary inputs. Whether all tripping and lockout relays are reset
– It gets resettled after the password but I want to bypass the password and reset the lockout through the push button or FnKey
– Assign a binary input (either FNkey or PB) to relay. According to connect in PSL. Could you please check Lockout reset instead of Rst CB1 lockout and Rst CB2 lockout?
– You can try to clear through supervision or From view records, reset indication .this will clear everything

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– As we know grid substations always have future scopes. If a very narrow margin of safety factor is given due to documentary error, how can we negotiate with them? We need standard
– I don’t think any standards are available about margin factor to be considered



– What is biased current in differential prot?
– I bias =( I1+I2) /2 or load current. I1 for HV and I2 for LV As per Micom p643 For Transformer diff protection
– It is available also for line and bus bar protection

– How to export settings in pdf Easergy studio?
– Open every carpet and select all that You need ( ctrl +clic) and after go to printer And click print as PDF

I just want to send a goose signal which block I should use for any user-defined signal in pcm600 2.10. What do u mean by block?
– Simply add the signal with OR gate in the input of Goose block
– Which block is used for goose send?
– You can use all these depending on your input type
– Is your input is the double point?
– The goose block in the Tx relay should be the same in the Rx relay for the 670 series
-Single point single
– I have 615 series

– In 30 kV switchgear if I put the incoming circuit breaker open and in service position I read voltage (700 V) in the relay. Is it new or it has been existing? Just to know whether this has just come up all of a sudden?
– I’m thinking that you may check the ratio set in a relay or if VTs are located on the cable side check whether no back feed, otherwise check whether there is a CB pole that is not opening wholly.
– It is a new MV switchgear and after tests, we tried to put it in service but when we put the incoming CB in test position we read voltage in the protection despite the CB is open.
– VT is located before the Breaker towards the incoming Cable, then check Relay power Data & compare it with SLD CT/VT data.
– There is not VT in the cable the VT is in the bus bare

– In measured is the earth fault current measured by the earth fault current coil of the relay? In derived is the earth fault current derived in relay by summation of Irph+ Iyph+Ibph currents?
– Sensitive protection will be used if the desired protection settings are very low for earth fault eg 0.001 x In.especially where the system is NGR earthed
– Vn derived is open delta voltage derived by relay during summation of Vr+Vy+Vb voltage. this is done when the 4th coil is not available in the relay. the summation is the vector summation
– This is a Neutral Displacement Relay.
– Yes, CBCT is used as sensitive protection (while earth fault current is very low).
– This is the Rated Operating Sequence (Duty Cycle) of the circuit breaker. This denotes the sequence of opening and closing operations which the circuit breaker can perform under specified conditions. The operating sequence as follows: O-t-CO-T-CO
– since CB is already charged it will take t= 0.3 s to close but next reclose order CB has to recharge its operating mechanism and it will take T= 3 min to recharge its spring or hydraulic system and then able to reclose. And 0.3 s is required for Arc Quenching medium such as oil, SF6, etc to regain its properties after tripping of the CB.
– What is the consideration to choose the reclaim time for CB reclosure by 3 min?
– Maybe Mechanical charging movement to avoid failure in the system when fail to reclose at 1st order. While 3 minutes is enough to decide what you have to do.
– In the case of 220kv Substation, when both lines are charged, then why bus coupler is closed?
– Ring Bus System (Loop). Is more dependable?
– Voltage collision may happen when the bus coupler is closed. You have to use Synchron check relay to close the bus couple breaker during both of buses is energizing
– By the use of only a syn check relay, the problem will be solved.
-What is the problem?
– Sequence, interlock, protection, synchronizer.
– yes I agree. It concerns mechanical charging i.e spring charge and also its insulation media, But isn’t 3 min is too long?


– I am trying to trace a fault on the Transformer that trips on differential protection. I conducted an IR test, it shows okay. I need advice
– Check the CT. CT Polarity & CT ratio should be the same. Please check the CT connection.
– No, sometimes when a problem at 1st order, you need to check all anatomy and the condition while that’s 3 min.


– As a thumb rule -Alternatively, the set differential relay shall have an offset of 20 per event of transformer full load current. This is just a thumb rule. U need to use ur judgment
– As the Last option, can u please carry out a stability check for through fault current condition?
– These are the three options available to verify differential relays. The most event is CT has saturated.
– Yes, one CT gets saturated due to through fault current in low impedance differential relays.
– Are u commissioning a new transformer (first charging), or is it a transformer that is already in service?
– It ready for service
– there is induction near the primary CT but, we are trying to isolate the area
– I have found the cause of tripping. It’s LV side VT
– What Vt is causing to trip?
– There is a breakdown of insulation between the HV side of the VT to ground

– What is the process of relay setting
– At first, you have to download the manual instruction. Then read it. And then you do copy the section of the setting & configure it in your own format of Work Instruction.
After that done, you will get the answer.
– We carry out an Insulation resistance test on each terminal equipment and finally found that the IR of VT is >10 kilo-ohms. We try to restore the Transformer but it is still tripping on differential protection after 3seconds
– It’s 7.5 MVA 132/33kV Transformer, CTR: pri = 100/1A sec=100/1A
– VT has primary terminal A-N. try to remove N which is connected to the body of the VT, and try the IR test. Secondary terminal a-n. Remove n from the earth and perform the following IR test.

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After all, the connection is installed properly, comprehensive CT needs to check, and or inject current test for the relay.
And also Transformer Ratio check.
-3 seconds is a lot of probability, I guess it was suspected since knee CT/saturated or relay accurate has been out of spec. Except for cable connection.
– 3 seconds means 3000 mili-second. This is too much.



– We have a problem with our plant. the design is based on 30MW for each power gen steam turbine and 4MW from the grid all protection and study state. know we bring 30MW from grid and 15MW for each TG we face à lot of problem like blackout when grid disturbance. the restudy is requested? and I need your advice, please
– There is a problem with relay coordination. you need to get your relay settings reviewed.
– Is ur plant getting islanded for grid disturbances?
– Yes
– Speed control check also
– Load share I mean Or speed droop?
– If ur plant gets islanded and TG’s are detecting the islanding. then TG sets should survive. since u are importing 30MW from the grid. please check the balance load on TG after islanding also
– What is the voltage level When I Will be on-site I Will share it With u sld?
– 60kv
– Island mode means autonom Without external source 60 kv
– What is the EDG rating (MW rating) and the other source details which u intend to run in parallel while carrying out EDG testing. what is the short circuit rating of a 6.6KV bus? how much time u intend to run in parallel. as we understand EDG is generally used for a black start may not continuously be in the circuit.
– Putting a reactor will increase the problem as it will be difficult for voltage control. That reason makes it interesting.
– Nothing related between Busbar rating with short circuit except failure in insulation, its mean busbar failure
– Maybe reactor installation initiated during EDG Chosphi gone to capacitive area. That problem in load share control/speed droop.

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