Plan of Filtering and VAR Compensation for Printing & Dyeing Industry

I. Hazards of harmonics:

1. When the harmonic currents and voltages injected into the PCC are in excess of the limits specified in GB/T 14549-93 Quality of Electric Energy Supply: Harmonics in Public Supply Network,the public grid will be contaminated.

2. Both the power supply and consuming equipment will not be fully functioning, giving rise to a waste of resources.

3. The input of a traditional capacitor set will generate parallel resonance with the system, severely jeopardizing operation safety of the system.

4. The regular capacitor sets will incur potential safety hazards when running with overcurrent or overvoltage under strong harmonics.

5. Leading to excessive temperature rise of transformers and aggravating both the active and reactive power loss, increasing the cost of power consumption of enterprises.

6. Interfering with the meters of electricity selling points, causing severe measurement errors.

7. Affecting production and long-term stability of power supply equipment.

II. Parameters of power supply equipment:

Transformer 1#          1,250 kVA          10/0.4          4.43% 

Transformer 2#          630 kVA             10/0.4          4.31%

Transformer 3#          630 kVA             10/0.4          4.23%

Now that 3 power transformers are in parallel and overloaded operation, the user will be required to perform harmonic suppression prior to apply for expansion. Therefore, a set of equipment for filtering and VAR compensation must be designed.

III. Design basis:

1. GB/T14549-93 Quality of Electric Energy Supply: Harmonics in Public Supply Network

2. GB/T15576 Low-Voltage Reactive Power Compensation Assemblies - General Technical Conditions

3. Data from this supervision and the past experience on suppression

IV. Targets of suppression:

Both the current and voltage harmonics injected into the PCC are in compliance with GB/T14549-93 Quality of Electric Energy Supply: Harmonics in Public Supply Network, and fulfill the requirements of normal operation of power supply and production equipment.

V. Elimination methods for harmonics:

● Using TSF (Thyristor Switched Filter) to implement fast, dynamic response compensation;

● Employing passive filtering to filter a considerable amount of current harmonics, thus reducing the harmonic voltage;

● Installing a filter and VAR compensator for the 0.4 kV side of the power supply transformer; and

● Excluding the existing capacitance compensators from operation.

VI. Design of TSF filtering compensator:

1. Technical indicators of TSFs

a. The filtering compensation system is connected to the secondary side of the rectifier transformer.

b. The absorption rate for 5th, 7th and 11th harmonic currents shall reach over 70%, and the harmonic voltages of the corresponding sequences shall conform to GB/T14549-93.

c. Response time no less than 20 mS.

d. Average power factor of compensation ≥ 0.90

e. Voltage fluctuations in the grid during compensation comply with GB/12326-90, i.e. the voltage fluctuation of the primary side as a result of variation from full to light load compensation ≤ 2.5%.

f. The compensation system is provided with the following operation security measures: System: overvoltage, overcurrent, undervoltage and grounding protection;

Capacitor: overvoltage, overcurrent, overheating and phase loss protection; 

inductance (reactance): overcurrent and overheating protection.

g. Total power consumption of compensation system: Ploss is smaller than 1.5% * Qtotal (where Qtotal is the total compensation).

h. The system generates no radio (radio frequency) EMI.

i. Operation modes: Fully automatic, operating continuously.

j. Parameter display: 11 kinds of data like PF, U, I, S, Q, P and working order.

VII. Determination of filtering compensation branches:

1.Computing formula: Q = P (-)

Where, Q - compensation capacity

           P - load power

   Cosф1 - power factor prior to compensation

   Cosф2 - target power factor after compensation

Since the existing capacitance compensation cabinet cannot be excluded, it can only be calculated as:

700 A * 380 * √3 ≈ 460 KVAr

The reckoned natural power factor is: 0.93 pf

In consideration of site conditions and the past experience on suppression, a certain margin of 800 KVAr is provided.

2. Determination of filtering and compensation loops

Through establishment of the abovementioned known and reckoned parameters, the harmonic compensation system is determined.And by amending the analog results for a couple of times, all loop parameters can be defined.

H5-1 1 filtering compensation branch                   250 KVAr of fundamental compensation capacity

H5-2 1 filtering compensation branch                   250 KVAr of fundamental compensation capacity

H7-1 1 filtering compensation branch                   100 KVAr of fundamental compensation capacity

H7-2 1 filtering compensation branch                   100 KVAr of fundamental compensation capacity

H11  1 filtering compensation branch                   100 KVAr of fundamental compensation capacity