ACREL AC energy meter's Application in PV system in Bulgaria

Abstract: This paper introduces the application of ackry APM series AC meter in the AC side of Bulgarian photovoltaic system. It is mainly used to measure the current in the photovoltaic system, and cooperate with the transformers to measure, communicate and control the circuit system.

1.Project Overview

The company is located in Bulgaria. The company is mainly engaged in the design / installation, construction / maintenance of small photovoltaic power generation center projects in Bulgaria and surrounding countries. The customer wants to use AC meters apm801, apm810 and mutual inductors for monitoring, metering and communication of current and voltage at the AC side of photovoltaic system, and control by using the switching value function of APM meter.

2.APM Series Energy Meters

APM series power meters of ACREL are power meters that are designed according to IEC standards and synchronized with international advanced technology.

APM series meters have full power measurement, energy statistics, analysis of power quality and network communications and other functions, are mainly used for comprehensive monitoring of the quality of power supply network.

This series of meters use a modular design, with a rich function of the external DI / DO module, AI / AO module, event recording (SOE) module with T-Flash (TF) card, network communication module, Temperature and humidity measurement module, can achieve full power measurement of electrical circuit and monitoring of switch status, Dual RS485 with Ethernet interface can realize data copying of RS485 master station, eliminating the need for data switching exchange. PROFIBUS-DP interface can realize high-speed data transmission and networking function.

3.Type and Function Description

Function			APM800 (class 0.5s)	APM801 (class 0.2s)	APM810 (class 0.5s)
Measured parameters	Total electrical measurement		√	√	√
Measured parameters	Four-quadrant energy		√	√	√
Pulse output of energy	Pulse output of active/reactive energy		√	√	√
Demand	Three-phase current, active power, reactive power, real-time demand of apparent power, and maximum demand (including time stamp)		√	√	√
Extreme value statistics	Extremum of current, line voltage, phase voltage, active power, reactive power, apparent power, power factor, frequency, total harmonic of current, total harmonic of voltage in this month and last month (including time stamp)		√	√	√
Power quality	Unbalance of current, line voltage, phase voltage		√	√	√
	Voltage phase angle, current phase angle		√	√	√
	Voltage current phase Angle		√	√	√
	Total (odd, even) harmonic content of voltage and current		×	×	√
	Harmonic content of voltage and current (2-63 times)①		×	×	√
	Voltage crest factor		×	×	√
	Telephone waveform factor		×	×	√
	Current K-factor		×	×	√
Alarm records	A total of 66 kinds of alarm types, each type can record the most recent 16 alarm records, support extended records by TF card		√	√	√
Event log	Record the most recent 128 event records, support extended records by TF card		√	√	√
Communication	Modbus protocol		√	√	√
I/O	2 digital inputs + 2 digital outputs (2DI+2DO)		√	√	√
Extensions	MD82	8 digital inputs + 2 digital outputs with changeover contacts (8DI+2DO)	√	√	√
	MLOG	TF card storage (alarm records, event records, electrical parameters and energy timing records, etc.)	√	√	√
	MA84	8 analog inputs (class 0.5) + 4 analog outputs (class 0.5) (8AI+4AO)	√	√	√
	MCM	1 RS485/Modbus-RTU, support master mode or slave mode	√	√	√
	MCP	1 Profibus-DP	√	√	√
	MCE	1 Ethernet, support Modbus-TCP, http, SMTP, DHCP protocol	√	√	√
	MTH	4 ways of temperature measurement, 1 way of temperature and humidity control	√	√	√

4. Technical parameters

Technical Parameters	Index
Signal	Electrical network	Three-phase three-wire, three-phase four-wire, see the wiring diagram;
	Frequency	45～65Hz；
	Voltage	Rated value：AC 100V、110V、400V、690V；
		Overload: 1.2 times rated value(continuous); 2 times rated value /1 second;
		Power consumption: < 0.5VA (per channel);
	Current	Rated value: AC 1A, 5A, support 4 mm2 line access;
		Overload: 1.2 times rated value(continuous); 10 times rated value/1 second;
		Power consumption: < 0.5VA (per channel);
Measurement accuracy	Voltage、current and power	class 0.5s/class 0.2s (APM800、APM810/APM801)
	Active power	class 0.5s/class 0.2s (APM800、APM810/APM801)
	Reactive power	class 2
	Harmonic	1%（2rd~42nd）、2%（43rd~63rd）
Switch inputs	Dry contact inputs, built-in power supply;
Relay outputs	Contact type: open contact in main part, changeover contact in module; Contact capacity：AC 250V/3A DC 30V/3A；
Pulse output of energy	Output mode: Optocoupler pulse with open collector; Pulse constant：4000（5A）、8000（1A） imp/kWh；
Analog outputs	DC 0mA～20mA、4mA～20mA、0V～5V、1V～5V output, accuracy class 0.5%, load resistance ≤ 500Ω;
Analog inputs	DC 0mA～20mA、4mA～20mA、0V～5V、1V～5V iutput, accuracy class 0.5%
Storage card	Standard Capacity:4G,TF Card Up to 32G Capacity;
Communication	RS485 interface/Modbus-RTU protocol and DLT645 protocol Profibus-DP interface/Profibus-DP protocol; RJ45 interface (Ethernet) / Modbus-TCP, http, DHCP and other protocols;
Power supply	Working range: AC/DC 85V～265V or AC/DC 115～415V(P2); Power consumption: Power consumption of the main part ≤ 15VA;
Safety	Power frequency withstand voltage	The power frequency withstand voltage between the shell and the auxiliary power supply, each input and output terminal group is AC 4kV/1min; The power frequency withstand voltage between the auxiliary power supply and each input and each output terminal group is AC 2kV/1min; The power frequency withstand voltage between the voltage input and other input/output terminal groups is AC 2kV/1min; The power frequency withstand voltage between the current input and other input/output terminal groups is AC 2kV/1min; The power frequency withstand voltage between the relay output and other input/output terminal groups is AC 2kV/1min; The power frequency withstand voltage between each terminal group of switch input, communication, analog output and pulse output is AC 1kV/1min;
	Insulation resistance	Inputs、outputs to the shell>100MΩ；
Electromagnetic compatibility	Meet IEC 61000 standard (Level 4);
Protection level	Display panel IP52
Environment	Operating temperature: -20 °C ~ +65 °C; Storage temperature: -20°C～+70°C; Relative humidity: ≤95% without condensation; Altitude: ≤2500m;
Standards	IEC 60068-2-1 IEC 60068-2-2 IEC 60068-2-30		Environmental Testing-Part 2-1:Tests Test A:Cold IDA Part 2-1:Tests Test B:Dry heat Part 2-30:Tests Test Db:Damp heat,cyclic(12+12h)
	IEC 61000-4	Electromagnetic compatibility-Testing and measurement techniques
	IEC 61557-12	Electrical safety in low voltage distribution system up to 1000V a.c. and1500V d.c –Equipment for testing,measuring or monitoring of protective measures- Part12： Performances measuring and monitoring devices(PMD)
	IEC 62053-22	Electricity metering equipment (a.c.)-Particular requirements - Part22:Static meter for active energy（class 0.2s and 0.5s）

5.Requirements from Customer

terms of reference from grid supplier:

（1）monitoring voltages: L1-N, L2-N, L3-N. Unominal = 230V;

（2）switching relay output at overvoltage: 2 steps:

Step 1: 110% of Unominal or 253V - delay 60 seconds (s) ;

Step 2: 115% of Unominal or 264V - delay 0.1s;

（3）switching relay output at undervoltage:

1-step; 80% of Unominal or 184V - delay 0.2s; Range of settings: U: 10-100% of Unominal, step not listed, maybe 1V ot 1%; Delay: 0.05 s to 3s, step - not listed, maybe 1s;

（4）switching relay output at overfrequency

1-step; 50.5Hz - delay 0.1s; Range of settings: F: 50-52.5Hz, step 0.1Hz; Delay: 0.1-0.5s, step - maybe 0.1s;

（5）switching relay output at overfrequency

1- step; 47.5Hz - delay 0.1s; Range of settings: F: 47.5-50Hz, step 0.1Hz; Delay: 0.1-0.5s, step - maybe 0.1s;

（6）Delay for recovering. When DO is on by some of previous reasons, there should be time delay after grid parameter(s) are back in nominal range(s). Time range 1-60s, step 1s

（7）Additional settings. (If they are possible).

5.1 When Unominal is lower than 60-70%, under and overfrequency monitoring can be disabled

5.2 When overfrequency/underfrequency is happened - the DO should not be recovered automatically, it should wait for some kind of manual/remote restore.

The above 7 items are the special needs of customers for the purchased products. Except that some requirements in point 7 cannot meet the needs of customers, other needs can be met. Basically solved the needs of customers.

6.Installation Picture