What is the effect of capacitor voltage rise effect when load shedding
What is the effect of capacitor voltage rise effect when load shedding
(OP)
HI everyone,
I am studying how to place capacitors in a 12kv distribution network and i have a couple of questions that i can't seem to answer with the literature i read.
Lets consider a simple example,suppose you place a fixed capacitor on a 12KV line that is compensating 3 loads. see attachemnt.
now if you want to determine the voltage rise that the capacitor causes , the literature says :
Voltage rise = Capacitor current * system reactance
Where sytem reactance is the reactance between the voltage source and the capacitor.
What i don't understand is : When one or 2 of the loads are put out of service. How does the load that is still in service expercience a higher voltage rise? Because the system reactance didn't change! and the capacitor current didn't not change also. How am i seeing this wrong?
The reason for his question is that the utility has placed a fixed capacitor in an area with residential loads, but when the network was reconfigured, where some load behind the capacitor where shed, some customers claimed to have experienced high voltages.As a result the banks where put out of service.
I want to find out an explanation dor this.
Thanks in advance
I am studying how to place capacitors in a 12kv distribution network and i have a couple of questions that i can't seem to answer with the literature i read.
Lets consider a simple example,suppose you place a fixed capacitor on a 12KV line that is compensating 3 loads. see attachemnt.
now if you want to determine the voltage rise that the capacitor causes , the literature says :
Voltage rise = Capacitor current * system reactance
Where sytem reactance is the reactance between the voltage source and the capacitor.
What i don't understand is : When one or 2 of the loads are put out of service. How does the load that is still in service expercience a higher voltage rise? Because the system reactance didn't change! and the capacitor current didn't not change also. How am i seeing this wrong?
The reason for his question is that the utility has placed a fixed capacitor in an area with residential loads, but when the network was reconfigured, where some load behind the capacitor where shed, some customers claimed to have experienced high voltages.As a result the banks where put out of service.
I want to find out an explanation dor this.
Thanks in advance






RE: What is the effect of capacitor voltage rise effect when load shedding
RE: What is the effect of capacitor voltage rise effect when load shedding
RE: What is the effect of capacitor voltage rise effect when load shedding
RE: What is the effect of capacitor voltage rise effect when load shedding
RE: What is the effect of capacitor voltage rise effect when load shedding
RE: What is the effect of capacitor voltage rise effect when load shedding
Knowing the sending end voltage and the receiving end real and reactive power, the voltage drop is calculated as:
ΔV = V1-V2 ≈ (P*R+Q*X)/V1
Now you have Qc, contributed by the cap banks, then
ΔV' = V1-V2 ≈ [P*R+(Q-Qc)*X]/V1
The difference on ΔV will be the voltage rise caused by the capacitors.
Regards,
RE: What is the effect of capacitor voltage rise effect when load shedding
yyoungengineers, is it possible to get the parameters of loads and the network and the capacitor(s) for an actual calculation of the voltage drop in the network?
Actually, the problem may be still more difficult, because, as yyoungengineers wrote, the capacitor current did not change !?
RE: What is the effect of capacitor voltage rise effect when load shedding
It is not possible to get the load precisely.
The data that is available includes transformer rating , line parameters, but the load is not monitored.
Several moment measurement are taken with the use of high voltage meters.
However, the loads are constantly fluctuating , therefore these measurements should be considered as approximations.
When i simulted different scenarios in ETAP i only got a voltage rise of a few hundredth.
Can you provide me some literature on the resonant phenomena? I don't wanna exclude nothing.
Thanks again
RE: What is the effect of capacitor voltage rise effect when load shedding
But if you already have carried out the calculations, then this guess of the resonance as the cause of the voltage rise may not be correct.
RE: What is the effect of capacitor voltage rise effect when load shedding
Now that i am trying to place capacitors into the network, i want to prevent such phenomena. Therefor i want to know what considerations should be made in such situations...
RE: What is the effect of capacitor voltage rise effect when load shedding
How big is your capacitor and how much voltage rise you think would make sense to you?
I suggest you check your local distribution code or standards apply to your area to find out the maximum voltage fluctuations is allowed!
A few hundreds, L-L or L-G? Say you have L-G 200V rise on your 12kV system, that is almost 3% voltage rise! I wouldn't be surprised if there are some customer's complaints, that's all depends on what tx tap set to and how sensitive of their equipment.
RE: What is the effect of capacitor voltage rise effect when load shedding
RE: What is the effect of capacitor voltage rise effect when load shedding
hr = sqrt(MVASsc/Mvarcap)
RE: What is the effect of capacitor voltage rise effect when load shedding
I did notice that your source doesn't look correct at 0MVAsc.
RE: What is the effect of capacitor voltage rise effect when load shedding
I have also came to that conclusion, the 150 KVAR bank will only raise the voltage with 0....%
I always thought that overcompensation leads to overvoltages, they seemed like a synonym to me.
please provide me an article where the difference is elaborated.
RE: What is the effect of capacitor voltage rise effect when load shedding