Application of ARTU four remote units in low-voltage intelligent power distribution

Abstract: For low-voltage distribution lines with many feeders, multi-function power monitoring instruments are used to achieve telemetry, remote signaling, remote control and electrical energy measurement and management, with high cost and large investment. This paper introduces an intelligent power distribution scheme based on ARTU four remote units, which implements remote measurement, remote signaling, remote control and remote pulse on terminal distribution lines. This solution has the advantages of low cost, low investment and easy installation and wiring, which is beneficial to the further promotion and application of low-voltage intelligent power distribution.

1 Introduction With the increasing emphasis on the assessment of life, property safety and electrical energy-saving management, the application of low-voltage power distribution that requires intelligent monitoring is becoming more and more extensive. At present, multi-function power monitoring instruments are used to remotely measure the current and energy of the low-voltage distribution circuit, remotely signal and record the closing and tripping status of the circuit breaker, and use the host computer software to control the circuit breaker through the instrument. Although this solution can meet the requirements of low-voltage intelligent power distribution, each feeder requires a monitoring instrument, which is costly and requires a lot of investment, making it difficult for users to bear.
This article introduces the addition of ARTU four remote units on the traditional low-voltage power distribution lines to achieve intelligent low-cost multi-loop monitoring of low-voltage power distribution.

2 Product features
ARTU four remote units include four specifications: telemetry unit, remote pulse unit, remote signaling unit, and remote control unit. The appearance is shown in Figure 1. It is installed with DIN35mm rail. The front end has two groups of signal lights with communication indication and signal running channel indication. There are two RS485 interfaces for communication, one for setting and debugging of general parameters, and the other for reading and setting "four remote" values. There is a dial switch window at the top of the product, and the product communication address and baud rate can be set through the dial switch. The auxiliary power supply is available in 24Vdc or 220Vac / dc. The power consumption of the whole machine is less than 5W, and the protection level reaches IP20. The product meets the standards of JB / T10388-2002 "General Technical Conditions for Intelligent Measurement and Control Node Products with Bus Communication", GB / T7261-2000 "Basic Test Methods for Relays and Devices" and GB / T13729-2002 "Remote Terminal Equipment" standards.

figure 1

3 Function and application of four remote units
3.1 ARTU-M32 telemetry unit
3.1.1 Product functions
ARTU-M32 can simultaneously adopt 32 AC or DC analog signals, such as 0-20mA ac, 0-5V dc, 4-20mA dc and other analog quantities. After AC / DC conversion, it communicates with the host computer via RS485 bus for data exchange. The 32-channel two-color indicator is used to indicate the current status of each input signal. The green light indicates the normal state, the red light indicates the emergency state, and the yellow indicates the warning state. The telemetry refresh rate is less than 1s and the accuracy is 0.5.
3.1.2 The application of the product takes the detection of the working current of 16 feeders as an example. The primary scheme is shown in Figure 2 (a). The current transformer uses AKH-0.66S low-voltage dual-winding transformer for current collection. The rated current on the primary side is 5A- 6300A, the secondary output has 2 windings, one group outputs 0-5A (or 1A), and 99T1, 6L and other pointer tables are used to display the current value locally, and the other group outputs AC 0-20mA, which is remotely transmitted to the ARTU-M32 unit For telemetry, see Figure 2 (b). The current measurement loop displays the corresponding current value of each feeder loop through the pointer table. The telemetry loop uses the communication port to remotely display the current value of each loop.

figure 2

3.2 ARTU-P32 remote pulse unit
3.2.1 Product function
The ARTU-P32 remote pulse unit collects 32 electrical energy pulse signals, connects with the host computer via RS485 bus for data exchange, and has the count value power-off protection function. The pulse width is greater than 10ms, and the maximum cumulative pulse number is 4294967296. The number of electrical energy pulses collected by the host computer divided by the pulse constant (imp / kWh) of the loop energy meter is the electrical energy data of the loop. The remote pulse unit also has GPS time adjustment function.
3.2.2 The application of the product takes the measurement of the energy of 32 feeders as an example. The energy meter adopts the DTM862-2 type. The primary scheme is shown in Figure 3 (a), and the secondary collection of energy pulses is shown in Figure 3 (b). Use traditional mechanical electric energy meter with pulse interface and use intelligent pulse receiving device to realize remote centralized meter reading function.

image 3

3.3 ARTU-K32 remote signaling unit
3.3.1 Product functions
ARTU-K32 can accept 32 active or passive contacts, convert digital signals into digital signals, and achieve data exchange with the host computer monitoring system through communication. The time required for 32 channels to scan for 1 week is 1ms, and 2000 groups can be recorded. Event capacity, with GPS time adjustment function.
3.3.2 Product application
One ARTU-K32 can monitor the working status of 8 motor circuits or 16 lighting circuits. Taking the monitoring motor circuit as an example, the primary scheme is shown in Figure 4 (a), which consists of an NS circuit breaker with auxiliary and fault contacts, an LC1 AC contactor, an LR2 thermal relay, and an AKH-0.66P protection transformer. Each motor circuit monitors 4 sets of nodes, namely circuit breaker closing and fault contacts, motor running (contactor) status contacts, motor thermal overload (thermal relay) contacts, and one ARTU-K32 monitors 8 motor circuits. See Figure 4 (b), the operation and stop of the motor are controlled by the on-site start-stop button, the red and green indicator lights on the spot display the working status of the motor synchronously, and the remote signaling unit can remotely display the motor's operation value by monitoring the action value of the contact of each component Working status.

Figure 4

3.4 Function and application of ARTU-J16 remote control device
3.4.1 Product functions
ARTU-J16 is connected to the host computer through the RS485 bus, as a remote relay output module, used to receive computer commands, perform remote control operation or automatic control of the system, a total of 16 relay outputs, relay contact capacity 5A / 250VAC or 5A / 30VDC, The remote control accuracy rate is 100%, and can record 1600 groups of event sequence records, with GPS time adjustment function.
3.4.2 Product application Take one ARTU-J16 to control 8-channel low-voltage feeder as an example, CM1 circuit breaker is equipped with motor operating mechanism. The primary scheme is shown in Figure 5 (a), and the control method is shown in Figure 5 (b). The start-stop button manually controls the closing and opening of each circuit breaker on site, and the remote control unit centrally controls the working state of the 8-circuit breaker through the communication interface to achieve the working mode of local and remote control of the circuit breaker.

Figure 5

4 Application example Take a project as an example, 32 low-voltage feeders need to be monitored and networked, of which 16 are lighting circuits and 16 are motor circuits. Each feeder needs to measure three-phase current and electric energy, and perform fault recording and prevention. Jump by mistake. The A-phase and C-phase currents of each feeder are collected by AKH-0.66S dual-winding transformer. The 32 feeders are measured and remotely measured by 2 ARTU-M32 telemetry units. The B-phase current defaults to the average value of A-phase and C-phase; The electric energy measurement of each feeder adopts DTM862-2 watt-hour meter. One ARTU-P32 is used to collect electric energy pulse signal and upload the data to realize unattended reading of electric energy. One ARTU-K32 is used to monitor the switching status of the 16-channel lighting circuit, and two ARTU-K32 are used to monitor the working status of the 16-channel motor circuit and achieve event recording. Use 4 ARTU-J16 to control the breakers of 32 feeders to prevent accidental tripping, and 1 ARTU-J16 to control the contactors of 16 motor circuits to control the motor running status.
When multiple ARTU networks are used, the A and B terminals of the last RS485 should be connected with a terminal matching resistor R to ensure communication impedance matching. The terminal matching resistance is generally between 120Ω-10kΩ, and the wiring is different terminal matching The resistance may vary. Connect the RS485 bus correctly and connect to the host computer. The host computer sends commands according to the protocol format according to the station number and baud rate of the module. At this time, the communication indicator of the module flashes, indicating that the module has received the command from the host computer and responded, that is, the communication has been established, as shown in Figure 6.

Image 6

The hardware cost of using this solution is as follows: 64 AKH-0.66S dual-winding current transformers, with an increased cost of about 10560 yuan, 2 ARTU-M32 telemetry units, cost 7200 yuan, and 1 ARTU-P32 remote pulse unit cost 3500 yuan , 3 ARTU-K32 remote signaling units, cost 10500 yuan, 5 ARTU-J16 remote control units cost 19500 yuan. The cost of 32 DTM862-2 is 8,000 yuan. If an intelligent network instrument is used to realize the above functions, ACR210E (measuring three-phase current and active energy, with communication interface) and 2DI / 2DO (2-way remote signal and 2-way remote control) are required. The motor circuit needs to be monitored. There are many parameters, and it needs to be equipped with 4DI / 4DO (4-way remote signal 4-way remote control) switch quantity module. The cost of 32 instruments is 85760 yuan, which is an increase of 44.7% compared with the first solution.

5 Conclusion
In December 2007, the National Relay Protection and Automation Equipment Quality Supervision and Inspection Center tested and tested the performance indicators, electromagnetic compatibility, and communication specifications of the ARTU four-remote unit products, which met the relevant requirements. This product has been used in engineering distribution monitoring systems such as Qinghai Oilfield Water Supply and Power Supply Company, Suzhou Taxation Building, Inner Mongolia Zhuanghuang Qilin Coal Mine, etc., which reduces investment costs and produces good social and economic benefits.

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