1. Introduction

1.1 Applications

As the development of electrical power system automation and the prevalence of unmanned power substations, the requirement of the automation of DC power system is getting higher and higher. The DC system monitor based on microprocessor, the core monitor and control unit of DC power system, is designed to meet this requirement and replace human being in the maintenance and management of DC power system. Its four telefunctions of “telemeasure, telecommunication, telecontrol and teleadjustment” and smart control on battery can fully meet the demand of unmanned or less-manned watch on DC power system in electric power system.

 

2. Performance and Features

2.1  The monitor adopts the mode of distributed measurement & control and centralized management. This design features a clear system hierarchy and the flexibility in capacity enlargement. The device based on microprocessor can fully monitor, measure and control charger modules, batteries and buses voltage and insulation condition, etc.

2.2  The monitor adopts a modulation design idea in which every unit works independently, so the reliability of DC system is improved and the maintenance and management of the system get easy.

2.3  Main processor adopts a 32-bit MCU with a multitask function, and it can work coordinately with other processors.

2.4  Input unit of switch state(on/off) signals is integrated in the monitor with 15 input channels, and if more are needed, other unit(s) shall be provided. The input unit has its own CPU and all input channels are isolated photo-electrically, which reduce greatly malfunctioning of input signals and improve the system reliability by quick and real-time and accurate processing.

2.5  Output unit of switch state(on/off) signals is integrated in the monitor with 7 output channels. A big DC 24V relay with high drive ability is fitted to control DC 220V data directly.

2.6  Good man-machine interface with touch screen ensures powerful online helps and configurations and convenient operations.

2.7  All kinds of real-time data, information state and alarm messages are explicitly displayed to ensure the user get a timely and accurate information of the system running status.

2.8  Watchdog circuit is applied to monitor the running of software, at the same time the software adopts software traps and multilevel data backup anti-interruption technologies to ensure the reliability of the system and the integrality of data.

2.9  The monitor provides RS232 and RS485 interfaces to communicate with upper system, and the user can select either one of them according to the need.

2.10 Online diagnosing and self recovery functions are available.

3 Technical Data

3.1 Main Parts and Technical parameters:

3.1.1 Input unit of switch state(on/off) signals:

3.1.1.1 Performance

1. IO ports of the main CPU are used to deal with input signals.
2. Photo-electrical isolation with a DC 3000V isolation voltage.
3. 15 input channels with Schmitt triggers, avoiding malfunctioning effectively.
4. Input impedance:3 kW, 0.5 W 

3.1.1.2 Function

Converting various contacts and signals of DC system into digital signals and transmit them to main CPU via IO ports.

3.1.2 Output unit of switch state(on/off) signals:

3.1.2.1 Performance

1. IO ports of the main CPU are used to deal with output signals.
2. Photo-electrical plus relay isolation with a DC 3000V isolation voltage.
3. 7 output channels with a big DC 24V relay with high drive ability to control DC 220V data directly, improving greatly the system reliability.
4.  The output contact breaking capacity is 20W in a DC loop with inductive load under the condition of 250V less, 0.5A less,and time constant 0.5 s±75 ms.

3.1.2.2 Functions

General alarms sent to central signal is controlled by main CPU,including AC fault alarm, rectifier or charger fault alarm, battery fault alarm, DC bus fault alarm, DC distribution feeder trip alarm and communication fault alarm.

3.2 Power Supply:

DC 220 V/ 110 V/ 48 V,80％-120％ range,with a ripple coefficient of 5％less.

3.3 Power Consumption:

40W less under normal running state

3.4 Communication data:

Baud Rates:1200 bps, 2400 bps, 4800 bps, 9600 bps, 19200 bps（Default:9600 bps）

Interfaces: RS232/RS485

3.5 Reliability:

   MTBF( Mean Time Between Failures) is more than 100000 hours.

3.6 Insulation performance:

Except communication loops, the insulated resistance between loop and ground is over 100MW.

3.7 Medium strength:

   AC3000Vrms or DC1000V, 1min

3.8 Electromagnetic compatibility performance:

The monitor can withstand a fast and transient-change interference of severity class 4 and passed 11 EMC type tests.

3.9 Mechanical performance:

Good strength capability which can withstand an oscillation or a shock of severity class 1.

3.10 Environmental requirements:

    Running ambient temperature:-10℃－+55℃, with an average daytime temperature less than 35 ℃.

   Storage Temperature: -20℃- +60℃

   Relative Humidity:maximum average monthly relative humidity is 90％ with an average minimum temperature 25℃ , and no moisture condensation occurs.

   Atmospheric pressure:80-110 kpa.