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THIS WAY OF
CALCULATION MATCH
THE FRENCH REACTIVE ENERGY INVOICE SYSTEM.
THEN, EACH COUNTRY MUST USE ITS OWN SYSTEM FOR THE CALCULATION.
From 1st November 1987, in France, the reactive energy
billing limit changed for all "tarif Vert" rate subscribers (LV or MV metering) to:
* tg φ = 0.4 or cos = 0.928: on the primary winding,
* tg φ = 0.31 or cos = 0.955: on the secondary winding.
For the calculation of the capacitor banks to be installed,
proceed using the following method:
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analyze the 5 electricity bills from November to March,
-
select the month for which the bill is the highest (kvarh to
be billed),
-
evaluate the number of hours of operation of the
installation every month in day-tariff and peak hours (generally 6 a.m. to 10 p.m. excluding
Sundays),
-
calculate the capacitor power Qc to be installed
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Qc = |
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kvarh
to be billed (monthly) |
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Nb. of
working hours (monthly) |
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* for LV metering, in the calculation of the kvarh to be billed, EDF
introduces a fixed rate transformer consumption by applying a coefficient
of 0.09 on the secondary winding tg φ calculated to obtain the primary
winding tg φ.
Example
Take the subscriber SMITH:
. highest reactive energy bill: December 87,
. number of kvarh to be billed: 70,000,
. monthly number of hours of operation: 350 hours (day-tariff + peak)
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Qc (bank to be
installed)
= |
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2
- CALCULATION FROM MEASURING ELEMENTS REAS
ON THE HV/LV TRANSFORMER SECONDARY WINDING/ PkW - COS φ
Example
Take a plant powered from an 800 kVA HV / LV subscriber statio which
would like to change the power factor of its installation to:
* Cos φ = 0.928 (tg φ = 0.4) on the
primary winding
* or Cos φ = 0.955 (tg φ = 0.31) on
the secondary winding
with the following readings:
• voltage: 400 V three-phase 50 HZ
• P = 475
• Cos (secondary) = 0.75 (or tg φ
= 0.88)
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Qc (bank to be
installed) = Pkw
(tg φ measured - tg φ to obtained) |
Qc = 475 (0.88 - 0.31) # 270 kvar
Note: the coefficient K = (tg φ
measured - tg φ to be obtained) is obtained easily from
the Cos φ values using the conversion
table.
3 - CALCULATION FOR
FUTURE INSTALLATIONS
For future installations, compensation is frequently
requested from the commissioning stage. In this case, it is impossible to calculate the bank using conventional methods
(electricity bill or measurements on-site).
For this type of installation, it is recommended to install a capacitor bank equal to approximately
25% of the nominal power of the corresponding HV / LV
transformer.
Example
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1000
kVA transformer => Q capacitor = 250 kvar |
Note : this type of ratio corresponds
to the following operating conditions:
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• 1000 kva
transformer |
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• real transformer
load = 75% |
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• Cos φ of load
= 0.80 |
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k = 0.421 (table) |
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• Cos φ to be
obtained = 0.95 |
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Qc = 1000 x 75 % x 0.80 x
0.421 = 250 kvar |
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4 - CALCULATION FOR
INDEPENDENT PRODUCERS (SMALL POWER STATIONS)
For this type of installation, the independent producer must
supply the electricity company with a quantity of reactive energy equal to at least 40% of its active energy production
during WINTER day-tariff and peak hours.
In this case, the calculation of the capacitor bank should account for:
• the on-load reactive consumption of the generator
• the on-load consumption of the LV / HV transformer (if applicable)
• the reactive energy to be supplied, or 40% of the active energy produced
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