A. An overview of the 1.1. Dc system grounding fault in power system is a kind of fault that is easy to occur and has great harm to power system. Whether it is positive or negative grounding, in the case of two-point grounding, it may cause protection misoperation or protection rejection, which will endanger the normal operation of the primary system.

A. An overview of the

1.1. Dc system grounding fault in power system is a kind of fault that is easy to occur and has great harm to power system. Whether it is positive or negative grounding, in the case of two-point grounding, it may cause protection misoperation or protection rejection, which will endanger the normal operation of the primary system.

1.2. Due to the complexity and dynamics of dc system, dc grounding fault is often difficult to locate. At the same time, due to the wide application of microcomputer protection and integrated automation system, the accuracy and safety of dc system grounding monitoring device are put forward.

1.3 pen-jyc dc system insulation on-line monitoring device balances the requirements of monitoring accuracy and operation safety, and can realize the detection of all kinds of ground fault, insulation drop, ring network state, ac series power, dc mutual series and other faults.

1.4. The device combines the ping-pong principle and passive monitoring principle in the active mode, and based on the parallel operation of multi-16-bit CPU, redefines the standard of dc system grounding fault monitoring level through the innovative distributed system architecture DADC and the advanced whole-system analysis SynSystem algorithm.

2. System is introduced

2.1. Functional features

Real-time monitoring system ac and dc voltage and alarm

Real-time monitoring system insulation and alarm

Real-time ground loop detection

System loop detection and diagnosis

Circuit insulation classification warning

Analysis of grounding history

Voltage balance function

2.2 ac and dc voltage monitoring

Host real-time monitoring system bus voltage to ground, including system voltage, positive to ground voltage, negative to ground voltage and ac series voltage and real-time display.

When the dc system fails and the system voltage is too high or too low to exceed the preset setting value, or the ac voltage exceeds the preset setting value, the LCD screen of the host computer will display the alarm information, and the voltage over-limit indicator light and the buzzer will alarm at the same time.

Alarm information can also be uploaded to the integrated automation system or the upper computer of the scheduling automation system through YX switching quantity and RS485 interface.

2.3 insulation monitoring

Host real-time monitoring system bus resistance to ground, including positive resistance to ground, negative resistance to ground and real-time display.

When the dc system fails and the positive and negative ground voltages are no longer balanced and exceed the preset setting value, the LCD screen of the host computer will display the alarm information and the system grounding indicator and buzzer will alarm at the same time.

Alarm information can also be uploaded to the integrated automation system or the upper computer of the scheduling automation system through YX switching quantity and RS485 interface.

2.4 ground detection

The host machine receives the characteristic state information of each circuit transmitted by the sub-machine in real time, and conducts intelligent analysis through pattern matching technology to distinguish different grounding states, eliminate the system charging pulse interference, fluctuation level interference and the influence of the loop, and finally accurately judge the grounding circuit and calculate the grounding impedance.

The grounding impedance value is displayed on the LCD screen and can be uploaded to the integrated automation system or the upper computer of the dispatching automation system through the RS485 interface.

2.5 loop diagnosis

Power dc loop is ubiquitous and brings great disturbance to the location of ground fault point. Host by the characteristics of each loop state information and the features of the built-in rules for artificial intelligence pattern matching, first introduced the concept of the loop index, to the faults existing in the system of the loop, abnormal loop, the system of double as spare power supply circuits, belt loop of the circuit, and the loop grounding loop, provide perfect loop state information, and display on the LCD screen. Can effectively help the operation and maintenance personnel accurately understand the current state of the dc system, quickly troubleshooting.

2.6 insulation warning

Since the detection accuracy of the main machine is very high, which can reach more than 500K, the long-term change trend of the ungrounded circuit can be determined by detecting the ground impedance of the ungrounded circuit, and the early-warning information of the circuit grounding can be provided.

Insulation reduction early warning and loop matching monitoring provide effective means for the diagnosis of the system.

2.7 historical records

System ac series current and grounding records will be automatically saved in EEPROM for reference. This record includes the date and time of the series current or grounding, the grounding impedance, the series current voltage, the grounding circuit and other information and can be saved after the power is lost.

Keep 1000 grounding records.

Ac series current is marked as "00 -- 0", and the single series voltage is v.

2.8 voltage balance

? When the ratio of positive and negative bus voltage of the dc system beyond the maloperation risk factor 1.222, voltage deviation compensation device inside through the bridge to a balanced state of voltage dc system, namely the positive of voltage and the negative of the ratio of the voltage is greater than 0.869, or negative of the ratio of voltage to the positive of voltage is less than 1.150.

3. Main indicators

3.1 monitored insulation impedance value range to the ground:

Grounding impedance: 0-50k

Insulation reduction: 51-500k

3.2 monitored voltage range:

Direct to ground voltage: 0-300v

Negative voltage to earth: 0-300v

Total system voltage: 0-300v

Ac series voltage: 0-300v

3.3 resistance to distributed capacitance interference of dc system:

More than 10000 uf

3.4 applicable dc system voltage level:

220V, 110V, 48V, 24V or other voltage levels proposed by the user

3.5 the number of dc circuits can be monitored:

Bus 500

3.6 ground impedance value of host connected to dc system:

More than 1000 K

3.7 voltage monitoring error:

Less than 0.5%

3.8 ground insulation alarm:

Output contacts with YX

3.9 system low voltage over-limit alarm:

198V (with YX output contact)

3.10 warning of over-limit of system voltage:

242V (with YX output contact)

3.11 standard RS232/RS485/RS422 interface

Interface with integrated automation system and scheduling automation system.

3.12 working environment temperature: - 30 ¡æ - + 50 ¡æ.

3.13 relative humidity: less than 96%

3.14 allowable ripple voltage coefficient of dc voltage: 2%

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