Product function

To meet the needs of users:

●Three-phase current unbalance regulation 

●Voltage support 

●Capacitive and inductive var compensation 

●Support other functional extensions 

Product model and meaning

Technical parameters

HKK-SPC selection zoom table

Note: 1. The Table calculated unbalanced current values when the transformer load rate is assumed to be 20%. 

 2. For accurate computing, refer to the following formula: Q = sqrt(Q无²+ Q不²)and then select the appropriate SPC capacity based on the Q value. Of which,

Q无²is reactive current, Q不² is unbalanced current and Q is the total current to be compensated. 

Power quality background for low voltage distribution transformer

1. Three-phase imbalance is serious 

Because the user side of 400V low-voltage distribution transformer system is almost single-phase load, and the power supply is not synchronism,the distribution transformer system is easy to appear three-phase imbalance, which seriously exceeds the standard. 

Table 1 Unbalanced Distribution of a Bureau on July 22 (2,202 sets)

Note: Unbalance = (I_max-I_min)/ I_max 

2. Low voltage conformity rate 

The power supply radius of 400V low-voltage distribution system is large, because of three-phase unbalance,the influence of high and low power consumption time is easy to lead to the voltage exceeding the limit value, which leads to the problem of low voltage at the end of power supply. 

Table 2 Voltage Qualified Rates in a Area

Note: Class A is 10kV bus voltage of 35kV substation; Class B is bus voltage of 35kV substation; Class C is 10k V subscriber voltage of special line; Class D is 380/ 220V subscriber voltage, of which 380V voltage and qualified rate are up to 98%. 

3. Low power factor

Packet-switched capacitors are widely used, which have compensation steps and poor compensation effect, and are prone to overcompensation or undercompensation. 

Table 3 Power Factor Statistics of Low-voltage Stations in a Area (under the condition of light load )

Table 4 Power Factor Statistics of Low-voltage Stations in a Area (under the condition of heavy load)

4. Low efficiency of transformers 

The distribution transformer overloading is serious, resulting in insufficient output, serious heating, loud noise, reducing the life of the

distribution transformer, and even burning-out of the distribution transformer. 

Table 5 Half-year Load of 315k VA Transformer in a Area

Note: The data in the table are the maximum loading rate and the each-phase current at the maximum loading rate in half a year. 

Working principle

1. Principle of three-phase unbalance compensation 

After HKK-SPC is opened, the system current is detected in real time by external current transformer (CT), and the system current information is sent to the internal controller for processing and analysis to judge whether the system is in an unbalanced state, and the current value of each phase to be converted for reaching the balance state is calculated, then the signal is sent to the internal IGBT to drive its action, and the unbalanced current is transferred from the phase with large current to the phase with small current, and finally to the state of three-phase balance.

2. Principle of voltage support 

HKK-SPC samples the voltage at the compensation point and transmits the voltage information to the internal DSP to determine whether the voltage at the compensation point exceeds the set value. When the voltage exceeds the upper limit of voltage regulation (Umax), the SPC outputs the inductive current and lowers the voltage; when the voltage is lower than the lower limit of voltage regulation (Umin), the SPC outputs the capacitive current and raises the voltage, finally making the each-phase voltage stable in the normal range.

var compensation principle

After the HKK-SPC is opened, the load current is detected in real time through the external current transformer (CT), and the var content of the load current is analyzed by the internal DSP calculation. Then the PWM signal generator gives the control signa to the internal IGBT according to the value set, which makes the inverter produce the var compensation current meeting the requirement, and finally realizes the dynamic var compensation. 

1. HKK-SPC compensation for capacitive var (vector graph) 

2. HKK-SPC compensation for inductive var (vector graph)

Product application

1. Product installation schematic diagram 

The HKK-SPC is mainly installed on the low-voltage side of the distribution transformer in the distribution station.

That is, between the transformer and the user load. 

2. Installation mode of HKK-SPC on the site

The installation method supports the holding rod and H-rod.

Characteristics 

1、Powerful functions

●Three-phase unbalance compensation function 

●Capacitive -1 ~ 1 reactive compensation function 

●Voltage compensation function 

●Support remote data transmission function 

2、Excellent compensation effect

●Real-time compensation, response time less than 15 milliseconds 

●HKK-SPC is an active compensation device, which uses modern power electronic components to form current source device. 

●From the mechanism, it avoids the resonance phenomenon of traditional capacitor components which is more stable and safe. 

●No harmonic generation, no secondary grid pollution 

●Bidirectional split-phase voltage compensation to improve voltage quality 

3、Full-control equipment, maintenance-free and labor-saving

●HKK-SPC adopts advanced power electronics technology and data processing technology, automatically detects the change of phase current in the grid system, calculates and emits the necessary compensation current in real time, so that the grid can reach the equilibrium state quickly. 

●The whole process is automatically completed by equipment, and does not need manual operation, greatly saving the human cost incurred from the operation of traditional compensation equipment 

4、Multi-protection, use in various poor environment

●The inner core equipment of HKK-SPC has various protection functions: over-voltage protection, under-voltage protection, over-current protection, short-circuit protection, etc. 

●The cabinet of HK-SPC has protective functions: low-voltage protection, lightning protection and leakage protection 

●IP level: IP44 

Product dimensions

1、HKK-SPC 35/50 4 4L

2、HKK-SPC 100 4 4L