Phoenix Contact SCK-C-MODBUS User manual

User manual
Solarcheck string monitoring

2013-06-14
PHOENIX CONTACT 105608_en_00
Solarcheck string monitoring
UM EN Solarcheck String Monitoring
00
Designation Order No.
SCK-C-MODBUS 2901674
SCK-M-I-8S-20A 2903241
SCK-M-I-4S-20A 2903242
SCK-M-U-1500V 2903591
User manual
Designation:
Revision:
This user manual is valid for:

PHOENIX CONTACT
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User group of this manual
The use of products described in this manual is oriented exclusively to:
– Qualified electricians or persons instructed by them, who are familiar with applicable
standards and other regulations regarding electrical engineering and, in particular, the
relevant safety concepts.
– Qualified application programmers and software engineers, who are familiar with the
safety concepts of automation technology and applicable standards.
Explanation of symbols used and signal words
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hazards. Obey all safety measures that follow this symbol to avoid possible in-
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There are three different categories of personal injury that are indicated with a
signal word.
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alert the reader to a situation which may cause damage or malfunction to the
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This symbol and the accompanying text provide the reader with additional in-
formation or refer to detailed sources of information.

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PHOENIX CONTACT
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105608_en_00 PHOENIX CONTACT 5
Table of contents
1 Introduction ................................................................................................................................9
1.1 Product overview................................................................................................... 9
1.2 Area of application................................................................................................. 9
1.3 General safety notes............................................................................................ 10
2 General notes on PV systems ..................................................................................................11
2.1 Typical structure of large PV systems and PV power stations ............................. 11
2.2 Data collection in large PV systems ....................................................................15
3 Solarcheck string current measurement with SCK-M-I-… ........................................................17
3.1 Safety notes for the device .................................................................................. 17
3.2 Function .............................................................................................................. 17
3.2.1 Current measurement .......................................................................... 18
3.2.2 Digital input ......................................................................................... 20
3.2.3 Analog input ......................................................................................... 20
3.2.4 Internal temperature measurement ...................................................... 21
3.3 Data acquisition and transfer ............................................................................... 21
3.4 Power supply ....................................................................................................... 22
3.5 Technical data ..................................................................................................... 22
4 Solarcheck string voltage measurement with the SCK-M-U-1500V .........................................25
4.1 Function............................................................................................................... 25
4.1.1 Voltage measurement .......................................................................... 25
4.1.2 Note on the parallel connection of multiple voltage measuring
devices in a system .............................................................................. 27
4.2 Data acquisition and transfer ............................................................................... 28
4.2.1 Representation of voltage values at the analog output ......................... 28
4.2.2 Step response time ............................................................................. 29
4.3 Power supply ....................................................................................................... 29
4.4 Technical data ..................................................................................................... 30
5 SCK-C-MODBUS Solarcheck communication module ............................................................31
5.1 Function............................................................................................................... 31
5.2 Data acquisition and transfer ............................................................................... 31
5.2.1 SCK-internal communication cycle ...................................................... 33
5.2.2 RS-485 communication ....................................................................... 33
5.2.3 Register addresses .............................................................................. 35
5.3 Power supply ....................................................................................................... 37
5.4 Technical data ..................................................................................................... 38

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6 Installation ................................................................................................................................39
6.1 Connection description........................................................................................ 39
6.2 Measuring category and notes on insulation ....................................................... 43
6.3 Control cabinet .................................................................................................... 43
6.4 Cabling ................................................................................................................ 44
6.4.1 Installation instructions ......................................................................... 44
6.4.2 Material requirements .......................................................................... 48
6.4.3 Cable lengths and conductor cross sections .......................................48
6.5 Installing the SCK-C-MODBUS communication module...................................... 49
6.5.1 Addressing the SCK-C-MODBUS communication module .................. 49
6.5.2 Connecting the SCK-C-MODBUS communication module .................. 52
6.6 Installing SCK-M-I-xx current measuring modules............................................... 54
6.7 Installing the SCK-M-U-1500V voltage measuring module ................................. 57
6.7.1 PE connection ...................................................................................... 58
6.7.2 Connecting the measuring module to the SCK-M-I-8S-20A
Solarcheck current measuring module ................................................. 59
6.7.3 Connecting the measuring module outside of the
Solarcheck device range ...................................................................... 60
6.7.4 Connecting voltage measurement ....................................................... 60
6.8 Power supply for the Solarcheck devices ........................................................... 61
6.8.1 Design of the power supply .................................................................. 61
6.8.2 Design of a separate power supply for the SCK-M-U-1500V
voltage measuring module ................................................................... 63
7 Startup .....................................................................................................................................65
8 Additional functions ..................................................................................................................67
8.1 Energy-saving mode............................................................................................ 67
8.2 Locate function .................................................................................................... 68
8.3 System calibration ............................................................................................... 69
9 Installation examples ...............................................................................................................71
9.1 Example 1 ........................................................................................................... 71
9.2 Example 2 ........................................................................................................... 72
9.3 Example 3 ........................................................................................................... 73
9.4 Example 4 ........................................................................................................... 74
10 Troubleshooting .......................................................................................................................75
10.1 Diagnostics and error removal............................................................................. 76
10.2 Additional notes................................................................................................... 82

Table of contents
105608_en_00 PHOENIX CONTACT 7
A Appendix ..................................................................................................................................85
A 1 Register tables .................................................................................................... 85
A 2 Accessories....................................................................................................... 110
A Appendix for document lists....................................................................................................111
A 1 List of figures .....................................................................................................111
A 2 List of tables ......................................................................................................115

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8PHOENIX CONTACT 105608_en_00

Introduction
105608_en_00 PHOENIX CONTACT 9
1Introduction
1.1 Product overview
Solarcheck is a modular monitoring system for photovoltaic systems. It consists of a com-
munication module (SCK-C-MODBUS, Order No. 2901674) and various measuring mod-
ules for current and voltage measurement.
The communication module collects the data from all connected measuring modules and
forwards it to a higher-level controller via Modbus RTU using an RS-485 connection.
At the same time, the connected measuring modules are supplied with power via the com-
munication cable (SCK BUS) between the measuring modules and the communication
module.
Figure 1-1 Solarcheck topology
1.2 Area of application
The Solarcheck device range is designed for use in medium to large PV systems and PV
power stations. Currents up to 20 A, reverse currents, and voltages up to 1500 V can be ac-
quired. Even at the lowest level of utilization (one communication device with maximum as-
signment of measuring device connections), it is possible to monitor 64 strings of a PV sys-
tem.
With an average string power of approximately 4 kW, it is therefore possible to monitor a
segment of approximately 250 kW with just this basic design.
Typically the communication devices in a PV system are positioned centrally in a control
room. The measuring modules are located in string combiner boxes in the field. The internal
communication protocol enables the connected measuring modules to be supplied with
power via the communication cable. As a result, an additional power supply is not required
for the measuring devices in the field.
ILC150 ETH
Order-No.:2985330
HW/FW:00/100
MACAddr.: 00.A0.48.04.09.C0
AUTOMATIONWORX
MRESET
RESET
RUN/PROG
PRG
STOP
1.1 2.1
1.2 2.2
1.3 2.3
1.4 2.4
1.1 2.1
1.2 2.2
1.3 2.3
1.4 2.4
1.1 2.1
1.2 2.2
1.3 2.3
1.4 2.4
1.1 2.1
1.2 2.2
1.3 2.3
1.4 2.4
LINK
Compact controller
Communication module
(for up to 8 measuring modules)
Measuring module for
current (8 strings)
Measuring module for
current (8 strings)
Measurement and
control technology
Data cable
Modbus
PV field
Measuring module for
current (4 strings)
Solar cablesData cables
Measuring module
for voltage

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10 PHOENIX CONTACT 105608_en_00
1.3 General safety notes
•Installation, operation, and maintenance may only be carried out by qualified electri-
cians. Follow the installation instructions as described. When installing and operating
the device, the applicable regulations and safety directives (including national safety di-
rectives), as well as generally approved technical regulations, must be observed. The
safety data is provided in this user manual and on the certificates (conformity assess-
ment, additional approvals where applicable).
•The devices are only to be used as described here. Phoenix Contact accepts no liability
if the devices are used for anything other than their designated use. Any use other than
the designated use may lead to malfunction or irreversible damage of the devices.
NOTE: Electrostatic discharge
The devices contain components that can be damaged or destroyed by electrostatic dis-
charge. When handling the device, observe the necessary safety precautions against
electrostatic discharge (ESD) according to EN 61340-5-1 and EN 61340-5-1.
NOTE: Degree of protection
The IP20 protection (IEC 60529/EN 60529) of the devices is intended for use in a clean
and dry environment. Install the module in housing with at least IP54 protection according
to EN 60529. The stated limits concerning mechanical or thermal loads on the modules
must not be exceeded.
WARNING: Risk of electric shock
Do not install voltage measurement while the system is in operation. High voltages may
be present in parts of the system even in diffuse daylight. Observe all statutory require-
ments for live working.

General notes on PV systems
105608_en_00 PHOENIX CONTACT 11
2 General notes on PV systems
2.1 Typical structure of large PV systems and PV
power stations
PV generator with central inverter
Figure 2-1 PV generator with central inverter
Generator with string inverters
Figure 2-2 Generator with string inverters
Inverters with and without an internal transformer are used in PV systems. This results in
various electrical characteristics which must be considered with regard to the design of the
system, cabling, the use of other devices, and the grounding concept.
Inverters with transformers, for example, can be arranged without grounding as well as with
grounding on the negative or positive side.
+
–
L
N
~
=
~
+
–
=
~
LN
=
~
=
~
+
+
–
–

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As illustrated in the example below, this results in the following possible voltage levels in the
system:
Figure 2-3 Voltage ratio with and without transformer
1: Transformerless inverter
2a: Inverter with transformer, without grounding
2b: Inverter with transformer, with grounding at negative pole
2c: Inverter with transformer, with grounding at positive pole
The diagram also clearly shows that using transformerless inverters can mean that the total
PV generator potential oscillates to ground, even though the generator voltage itself sup-
plies a DC voltage.
In the case of transformerless inverters, it should also be noted that there is no electrical iso-
lation to ground here. This is particularly important if devices are incorporated in the system
which are only intended for IT systems, i.e., they have no ground connection.
Example diagram of generator with transformer inverter
Figure 2-4 Example diagram of generator with transformer inverter
-800
-600
-400
-200
0
200
400
600
800
1000
12a2b2c
V
PV
VDC
Filter Filter
H-Bridge
50 Hz
+
–
VAC
IAC

General notes on PV systems
105608_en_00 PHOENIX CONTACT 13
Example diagram of generator with transformer inverter and grounding on the pos-
itive side
Figure 2-5 Example diagram of generator with transformer inverter and grounding on
the positive side
Example diagram of generator with transformer inverter and grounding on the neg-
ative side
Figure 2-6 Example diagram of generator with transformer inverter and grounding on
the negative side
+
–
L
N
~
=
~
+
–
L
N
~
=
~

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Example diagram of generator with transformerless inverter
Figure 2-7 Example diagram of generator with transformerless inverter
The individual strings of a PV generator, particularly in large systems with central inverters,
are connected in so-called string combiner boxes. In these string combiner boxes, multiple
PV strings are connected together in parallel and appropriate protective devices and moni-
toring devices are provided.
When creating your PV system, observe the necessary standards for planning and installing
PV systems, such as IEC 60364-7-712, together with corresponding references and equiv-
alent standards.
VDC
Filter Filter
H-Bridge
IAC
VPV-PE

General notes on PV systems
105608_en_00 PHOENIX CONTACT 15
2.2 Data collection in large PV systems
Figure 2-8 Data collection in large PV systems
Data collection in large, extensive PV systems presents a challenge with regard to the net-
work technology. On the one hand, the reliable assignment of data and data security must
be implemented well; on the other hand, the hardware design needs to be inexpensive and
straightforward. This is particularly relevant in the special electrical environment of a PV
power station.
Although the PV generator generates a direct current in principle, the inverters in the system
likewise have an impact on the power cables. This means that in a PV system, the inverter's
method of operation generates AC voltage components on the DC side. This may lead to
inductive interference of cables and devices in the proximity of the generator's DC cabling.
Depending on the inverter type and connection, the effect of these AC voltage components
can vary.
In order to avoid any influence on signals and data cables, corresponding standards regard-
ing the installation of data cables in the vicinity of power cables must be observed. Standard
DIN EN 50174 provides comprehensive guidelines on planning and installing communica-
tion cables in the vicinity of power cables.
Weather Station
Data Storage
Remote Visu
Inverter Station
Local Visu
Internet
PV Plant Main cabinet Infrastructure
StringBox
Signal conditioning
(PLC Function)
Energy
Data
StringBox

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Solarcheck string current measurement with SCK-M-I-…
105608_en_00 PHOENIX CONTACT 17
3 Solarcheck string current measurement with SCK-M-I-…
Various device versions are available for string current measurement. The device designa-
tion indicates the number of current measuring channels and their measuring range final
value. Hall sensors are used for contact-free current measurement. The devices also have
a digital input, internal temperature indication, and some have an analog interface for con-
necting a Solarcheck voltage measuring device.
3.1 Safety notes for the device
•Do not open or modify the device. Do not repair the device yourself; replace it with an
equivalent device. Repairs may only be performed by the manufacturer. The manufac-
turer is not liable for damage resulting from noncompliance.
•The termination area must be covered after installation to ensure sufficient protection
against accidental contact with live parts (e.g., installation in a distributor box or control
cabinet).
3.2 Function
Table 3-1 Function matrix for current measuring modules
SCK-M-
I-8S-20A
x-xxxxx
SCK-M-
I-4S-20A
-xx-xxx
Module
8-channel current measurement up to 20 A
4-channel current measurement up to 20 A
Reverse current detection
Analog input for voltage measuring devices
Digital input
Internal temperature measurement
Power supply via SCK-C-MODBUS
Block diagram
SCK-
BUS
OUT
U-IN
Digital
IN
1
+
–
2
3
4
5
6
7
8
I-IN
μ
C
COM
8x
0...10V
1
2
3
4
I-IN
m
C
SCK-
BUS
OUT COM
4x
Digital
IN

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3.2.1 Current measurement
Hall sensors are used for contact-free current measurement. For measurement purposes,
the PV string cables are led through the holes in the module in the specified direction. Each
channel is equipped with a separate sensor. This means that all connected strings can be
measured independently of one another.
Figure 3-1 Channels for current measurement/feed-through direction
The channel assignment is printed on the side of the housing.
Figure 3-2 Assignment of the current measuring channels
Hall sensor measuring technology
The cable feed-throughs in the device are surrounded by magnetic cores which absorb and
concentrate the magnetic field of the live conductor. A Hall sensor positioned in an air gap
in the magnetic core generates a voltage signal proportional to the strength of the magnetic
field. This voltage signal can then be used directly to determine the current strength. Since
the current direction also determines the direction of the magnetic field, this measuring tech-
nology can also be used to indicate the current direction. As a result, reverse current detec-
tion is integrated in the Solarcheck current measuring devices.
P_OUT
SCK-M-I-8S-20A
Order No. 2903241
P
SCK BUS D_IN
TX
0...10V
U
OUT
U
IN
0...10V
GND2
GND1
STRING
CURRENT
SCK-M-I-4S-20A
Order No. 2903242
P
SCK BUS D_IN
TX
STRING
CURRENT
78
5
2
3
6
1
4
2
4
1
3

Solarcheck string current measurement with SCK-M-I-…
105608_en_00 PHOENIX CONTACT 19
Value ranges
Reverse currents of up to -1 A can be measured. Positive and negative current values are
stored in a signed register. The values can be interpreted and a corresponding alarm func-
tion can be activated via a higher-level controller.
Values outside the measuring range from -1 A to +20 A are not accurate enough. Values
outside the overcurrent range from -1.5 A to +25 A are removed from the register.
Figure 3-3 Valid value range for current measurement
Measuring accuracy
Current measurement has an accuracy of ±1%. This value is based on the measuring range
final value (20 A) and is valid for the entire measuring range from -1 A to +20 A. Further-
more, a temperature coefficient TC20 is applied to the measurement. This is ±0.02%/Kelvin.
The deviation occurs above and below the production-related compensation temperature
of 20°C.
Example:
Ambient temperature: 30°C
Deviation of measurement ±1% + (±0.02% x (TAmbient – TCompensation))
Deviation at T30°C = ±1.2% of measuring range final value (±1.2% of 20 A = ±240 mA)
I
String‘
I
String
0 A-1,5 A -1 A 1 A 25 A
20 A 100 A
25 A
20 A
-1 A
-1,5 A

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3.2.2 Digital input
Wire floating contacts of, e.g., door contacts or remote indication contacts of surge protec-
tion elements directly to digital input D_IN.
The state of the switch contact is set as a bit in the communication module and can be read
by a controller.
Figure 3-4 Digital input
The refresh time for this status monitoring depends on the SCK-internal communication
loop. For additional information, please refer to “SCK-internal communication cycle” on
page 33.
3.2.3 Analog input
The analog input is designed for analog 0 … 10 V standard signals. Incoming 0 … 10 V sig-
nals are stored as a 16-digit INT value.
Using the analog connection for devices in the Solarcheck device range
The 2 … 10 V analog output of the voltage measuring module can be connected to the an-
alog 0 ... 10 V input of the 8-channel current measuring module. Use of this function is op-
tional. Due to the live zero point of the output, cable break detection is integrated automati-
cally (“live zero”). Output P_OUT is designed specifically for connection of the SCK-M-U-
1500V voltage measuring module (Order No. 2903591). The maximum distance between
current and voltage measuring modules is 0.5 m.
The value range is defined as -2000 … 12000 (for -2 ... 12 V). For further details on voltage
measurement, refer to Section 5.2.
NOTE: Risk of material damage due to incorrect wiring
The digital signal input may not be wired to an active signal.
SCK-M-I-8S-20A
Order No. 2903241
P
SCK BUS D_IN
TX
1214 11
FM
VAL-MS...
L– / L+