SMA Sunny String Monitor - Cabinet Quick start guide

Sunny String Monitor - Cabinet (SSM-C)
Installation and use of the SSM-C
Technical Description Version 1.0 SSMC-TEN072310
98-4000210

SMA Technologie AG
Technical Description SSMC-TEN072310 Seite 1
Index
1 Notes on this Manual. . . . . . . . . . . . . . . . . . . . . . 3
1.1 Validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Target Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Explanation of the Symbols Used . . . . . . . . . . . . . . . 3
2 Description of the Sunny String Monitor Cabinet . 5
3 General Safety Instructions . . . . . . . . . . . . . . . . . 7
3.1 Appropriate Usage. . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Personnel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4 Checking the Delivery . . . . . . . . . . . . . . . . . . . . . . . 8
3.5 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.6 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.7 Special Hazards of Photovoltaic Systems . . . . . . . . . 8
3.8 Special Hazards of Grounded PV Systems . . . . . . . . 9
3.9 Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.10 Electrical Connection . . . . . . . . . . . . . . . . . . . . . . 10
3.11 Disconnection. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.12 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.13 Commissioning, Maintenance and Repair . . . . . . . . 13
3.14 General Information . . . . . . . . . . . . . . . . . . . . . . . 13
4 Parallel Connection of Strings . . . . . . . . . . . . . . 14
4.1 Maximum Number of Strings per Measurement Input 14
4.2 Reverse Current . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5 Structure of the SSM-C . . . . . . . . . . . . . . . . . . . . 16
6 Installing the Floor-mounted Distribution Board . 18

SMA Technologie AG
Seite 2 SSMC-TEN072310 Technical Description
7 Connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.1 Connection of the DC String Lines . . . . . . . . . . . . . 21
7.2 Connection of the DC Main Lines . . . . . . . . . . . . . . 22
7.3 Ground Connection . . . . . . . . . . . . . . . . . . . . . . . 23
7.4 RS485 and Power Supply Connections. . . . . . . . . . 24
7.4.1 Cable Type for the Data Line. . . . . . . . . . . . . . . . . . . . . . . . . .24
7.4.2 Shield Contact Connection . . . . . . . . . . . . . . . . . . . . . . . . . . .24
7.4.3 Data Line Connection in the SSM-C . . . . . . . . . . . . . . . . . . . . .25
7.4.4 SSM-C Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
7.4.5 Connection in the Sunny Central . . . . . . . . . . . . . . . . . . . . . . .28
8 Configuration of the Sunny Central . . . . . . . . . . 32
8.1 Sunny Data Control . . . . . . . . . . . . . . . . . . . . . . . 32
8.2 Serial Interface Settings. . . . . . . . . . . . . . . . . . . . . 32
8.3 Detection of SSM-Cs. . . . . . . . . . . . . . . . . . . . . . . 33
8.3.1 Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
8.3.2 Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
8.3.3 Setting the Device Address . . . . . . . . . . . . . . . . . . . . . . . . . . .35
8.4 Deleting Detected SSM-Cs. . . . . . . . . . . . . . . . . . . 37
9 String Current Monitoring Function . . . . . . . . . . 38
9.1 Activation of String Current Monitoring . . . . . . . . . . 38
9.2 Polling Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
9.3 Error Sum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
10 Setting String Current Monitoring Parameters . . 41
10.1 Triggering Time . . . . . . . . . . . . . . . . . . . . . . . . . . 41
10.2 Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
10.3 Configuring Groups . . . . . . . . . . . . . . . . . . . . . . . 43
10.4 Setting the Number of Strings . . . . . . . . . . . . . . . . 45
10.5 Time Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
10.6 Overnight Shutdown Setting . . . . . . . . . . . . . . . . . 50

SMA Technologie AG
Technical Description SSMC-TEN072310 Seite 3
10.7 Setting the Anti-Theft Protection. . . . . . . . . . . . . . . . 51
11 Values of the String Current Monitoring System 53
11.1 Groups' Mean Values . . . . . . . . . . . . . . . . . . . . . . 53
11.2 Measured Values of the Measuring Channels . . . . . 54
12 Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
12.1 Active Warnings. . . . . . . . . . . . . . . . . . . . . . . . . . 55
12.2 Warnings History . . . . . . . . . . . . . . . . . . . . . . . . . 55
13 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . 56
13.1 Problems when Detecting the SSMs . . . . . . . . . . . . 56
14 Contact. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

SMA Technologie AG Notes on this Manual
Technical Description SSM-TEN072310 Page 3
1 Notes on this Manual
1.1 Validity
This documentation describes how to install and operate a Sunny String Monitor
Cabinet (SSM-C).
1.2 Target Group
This documentation is intended for installers and operators of PV systems which are
realized with the SSM-C. It includes a description of how to install, operate and
maintain the SSM-C, as well as troubleshooting with the aid of the Sunny Data Control
software and the data logger Sunny Central Control.
1.3 Explanation of the Symbols Used
In this document, the following terms and symbols are used to describe different hazard
levels:
DANGER!
DANGER indicates a hazardous situation which, if not avoided, will result in
death or serious injury.
WARNING!
WARNING indicates a hazardous situation which, if not avoided, could result
in death or serious injury.
CAUTION!
CAUTION indicates a hazardous situation which, if not avoided, could result
in minor or moderate injury.
NOTICE!
NOTICE indicates a situation that can result in property damage if not
avoided.

Notes on this Manual SMA Technologie AG
Page 4 SSM-TEN072310 Technical Description
Information
Information provides tips that are valuable for the optimal installation and
operation of your product.
Storage of handbooks
This operating manual, the installation guide, the data sheets, the operating
manuals of installed components, and the wiring diagrams must be kept in the
immediate vicinity of the Sunny Central. They must be available to operators
and maintenance staff at all times.

SMA Technologie AG Description of the Sunny String Monitor Cabinet
Technical Description SSM-TEN072310 Page 5
2 Description of the Sunny String Monitor Cabinet
The Sunny String Monitor Cabinet (SSM-C) enables connection of several strings in
parallel. If failures occur in individual modules, or in the string cabling, they can only
be detected with great effort, or not at all. The SSM-C reliably detects failures, and thus
prevents power losses and yield losses.
In addition, the SSM-C enables monitoring of the internal overvoltage protectors. They
are integrated into each SSM-C in order to protect the inverter from transient
overvoltages. The upstream string fuses allow defective strings, e.g. with a short circuit
in a module or the cabling, to be isolated from the entire PV array. If a string fuse is
triggered, this is detected by the software, and a warning is generated in the Sunny
Central Control (SCC), which is situated within the Sunny Central (SC). In addition, the
individual string currents are analyzed and displayed in the SCC.
For maintenance work and the connection of string lines, there are isolation terminals
in the SSM-C, which enable load-free disconnection of the individual connected strings,
or all connected strings, from the PV generator. An optional load-disconnecting switch
is available, which realizes disconnection from the inverter. See the block circuit
diagram of the SSM-C below.
Data transfer to the SCC occurs via an RS485 bus. The +55 V supply comes from the
Sunny Central.
Overvoltage
protection
RS485 +55 V
Sunny String Monitor Cabinet
String
current monitoring
Sunny Central
Sunny
Central
Control via
hub
Load
disconnector

Description of the Sunny String Monitor Cabinet SMA Technologie AG
Page 6 SSM-TEN072310 Technical Description
Essential differences to the previous Sunny String Monitor:
• Measurement in the negative and positive lines by means of variant configuration
• Only suitable for grounded systems
• Suitable for 1000 V DC
• Night operation possible for anti-theft protection
• Star-shaped RS485 wiring, with a maximum individual length of 1000 m
• Better troubleshooting and commissioning in the field due to star-shaped wiring
• Improved communication quality due to maximum of 5 participants per bus
• SSM-C power supply with safety extra-low voltage from the hub in the SC
• Communication and power supply are incorporated in one cable

SMA Technologie AG General Safety Instructions
Technical Description SSM-TEN072310 Page 7
3 General Safety Instructions
Failures that affect or limit the safety of the device must be rectified immediately.
Unauthorized modifications and the use of spare parts not recommended by SMA
Technologie AG may cause fire, material damage and electrical shock. Unauthorized
personnel must not have access to the equipment.
Warning signs must always be clearly readable and immediately replaced if damaged.
3.1 Appropriate Usage
Appropriate use of the SSM-C means following all instructions in the manual relating to
installation, electrical connection, and commissioning of the equipment.
Any deviation from the instructions in this manual is regarded as inappropriate use of
the equipment. SMA Technologie AG accepts no responsibility or liability for any and
all damage resulting from inappropriate use of the equipment.
Appropriate use of the equipment also entails the following:
• Observation of the safety instructions listed here and in the following sections
• Observation of the instructions in the Sunny Central installation guide and user
manual
• Conformance to the device-dependent technical data
Adherence to the additional notes for Sunny Central M/P inverters for grounded
operation of the PV generator
3.2 Personnel
Only qualified technical personnel may perform any and all work on the SSM-C.
"Qualified" means that the personnel must possess training relevant to the activity
performed and must be familiar with the content of this manual. The personnel must
have read and understood the safety section in this manual.
3.3 About this Manual
This manual was written with the greatest possible care. However, discrepancies cannot
be excluded. SMA Technologie AG accepts no responsibility or liability for injury to
persons, or material damage caused by mistakes in this manual.

General Safety Instructions SMA Technologie AG
Page 8 SSM-TEN072310 Technical Description
3.4 Checking the Delivery
On receipt of the equipment, check the packaging and the device for any possible
damage and compare the contents of the delivery with the delivery documentation. In
the case of damage to the device and/or unclear delivery contents, contact SMA
Technologie AG immediately (contact address is in the appendix).
3.5 Storage
The SSM-C may only be stored in rooms protected from dust and moisture.
3.6 Installation
The requirements relating to the installation location, the manner of installation and the
mounting position must be observed.
In addition to this, the following points must be noted:
• The installation location must be easily accessible and offer a secure base for
working on the device.
• The connection cables must be connected to the internal strain-relief clamp in the
base in order to prevent exertion of mechanical strain on the housing.
• Interference testing occurred as per DIN EN 61000; accordingly, the installation
location must be in an area where EMI fields are slight.
The SSM-C is built using the latest technology, and according to recognized safety
standards. Despite this, a fault resulting in arcing cannot be ruled out (see section 3.7
"Special Hazards of Photovoltaic Systems", page 11).
This can result in melting of the housing as well as fire and smoke, which represents a
hazard to personnel or equipment. This must be taken into consideration upon
installation.
• The equipment may not be installed near to inflammable materials. If this cannot
be avoided, preventative measures must be taken, which prevent fire and smoke
from spreading.
• The equipment may not be installed in critical areas, escape routes, living spaces
or office spaces.
3.7 Special Hazards of Photovoltaic Systems
DANGER!
Risk of lethal electric shock
An active power source is connected!

SMA Technologie AG General Safety Instructions
Technical Description SSM-TEN072310 Page 9
Photovoltaic systems have special characteristics representing special hazards that are
described here.
An active power source is connected, which means that depending on the operating
mode there may be voltage present, from the photovoltaic generator and/or the Sunny
Central. This is especially important to note when disconnecting the Sunny String
Monitor's floor-mounted distribution board.
Very high DC voltages are present (no zero-crossing) that, in the case of a fault or
inappropriate use of fuses or plugs, may lead to arcing.
The short-circuit current of the photovoltaic generator is only slightly higher than the
maximum operating current and is also dependent on the level of solar radiation, which
means that if a short circuit occurs in the system, the existing circuit breakers are not
guaranteed to switch off.
A highly branched generator array may be difficult to disconnect if a fault develops
(e.g. short circuit). We recommend the additional use of the optionally available DC
circuit breaker for disconnecting the inverter.
3.8 Special Hazards of Grounded PV Systems
The positive or negative pole of the PV generator is grounded within the Sunny Central
via a GFDI fuse (GFDI: ground fault detection interruption).
The grounding of the PV generator can be interrupted automatically by the GFDI at any
time.
NOTICE!
Additional grounding within the PV generator or floor-mounted distribution
board is not permissible!
NOTICE!
Refer to the additional notes for Sunny Central M/P inverters for grounded
operation of the PV generator.
CAUTION!
The GFDI does not ensure personal protection, but merely system protection!

General Safety Instructions SMA Technologie AG
Page 10 SSM-TEN072310 Technical Description
3.9 Cabling
With regard to the SSM-C cabling, it must be ensured that the data lines and the DC
main lines are laid separately. The distance between these two lines should be > 1 m.
In the event of damage to the high voltage line, dangerous voltages can couple into
the cable shield.
In addition, the data line's cable shield must be connected at both ends, i.e. in the SC
and in the SSM-C.
3.10 Electrical Connection
The electrical connection must be performed according to this manual and the device's
technical data.
DC Power Supply
Insertion of the string fuses and connection of the isolation terminals causes the DC
voltage of the connected strings to become available in the device.
The string fuses may only be inserted when the following conditions are satisfied:
• All connections are made according to this manual
• The load-disconnecting switch is deactivated, and the isolation terminals are open
• The DC main lines are connected to the inverter or DC distribution box and are
isolated (no reverse voltage is possible from the inverter).
• The polarity of the DC voltages at the string inputs has been checked, and there is
no short circuit present
• The strings have been checked with an insulation test to ensure that there is no
ground fault
NOTICE!
When cabling, ensure that the DC main lines and the data line are laid
separately.
WARNING!
The equipotential bonding must be connected!

SMA Technologie AG General Safety Instructions
Technical Description SSM-TEN072310 Page 11
3.11 Disconnection
The SSM-C must be disconnected for working at the SSM-C and at the SMU boards.
The device must be disconnected on both sides, i.e. the DC main lines to the SC via the
load-disconnecting switch, and the connected strings via the isolation terminals for PV
plus and PV minus. If there is no DC circuit breaker on the floor-mounted distribution
board, the DC fuses in the Sunny Central must be pulled in order to avoid reverse
voltage from the inverter.
Work carried out on the SMU board which, for example, involves unplugging the plug
connectors or removing the string fuses, is strictly only permissible under voltage-free
conditions.
WARNING!
If the isolation terminals are closed, the lower fuse holders are also energized
when the string fuse is disconnected!
The Plexiglas covers must always be mounted, to ensure protection against
accidental touching!
WARNING!
Before inserting the string fuses, the correct polarity and ground fault protection
must be ensured. The fuses may only be inserted or removed under load-free
conditions and using the appropriate personal protective equipment.
WARNING!
The isolation terminals may only be closed or opened under load-free
conditions.
WARNING!
Be careful of reverse voltage from the inverter!

General Safety Instructions SMA Technologie AG
Page 12 SSM-TEN072310 Technical Description
Capacitor Discharge Time
The device contains capacitors that discharge slowly when the device is disconnected.
There are dangerous accidental-contact voltages present in the device immediately
after switching off. If there is a fault in the device, these voltages may also remain
present for a longer period of time. For this reason, always check that the device is
voltage-free before working on it.
Information
We recommend the use of DC circuit breakers (optionally available) for
isolating the inverter or the SSM-C. Even in the case of faults or fire, this allows
system components to be isolated safely.
Information
Work on the SSM-C may be performed only after switching off the power to
the unit. The VDE regulations must be followed.
• Disconnect the device
• Protect against reenergizing
• Test each unit to ensure that all voltages have been removed
• If necessary, cover or protect against accidental contact with any voltage-
carrying components.
WARNING!
If the isolation terminals are closed, the lower fuse holders are also energized
when the string fuse is disconnected!
CAUTION!
The discharge time of the capacitors is longer than 5 minutes.

SMA Technologie AG General Safety Instructions
Technical Description SSM-TEN072310 Page 13
3.12 Operation
Apart from the optionally available DC circuit breaker, and the isolation terminals for
PV plus and PV minus, there are no other control elements on the floor-mounted
distribution board. Setting of parameters and querying of measurements occurs over the
RS485 serial interface. The device must only be opened for commissioning,
maintenance and troubleshooting. Observe the following safety instructions for working
on the device.
3.13 Commissioning, Maintenance and Repair
All work on the SSM-C may only be performed when the device is safely disconnected
from the PV voltage, when the device is secured against accidental restarting, and when
the device has been checked to be voltage-free. Only qualified technical personnel,
who are familiar with the operation of the system, may undertake any such work.
During maintenance, the ventilation plates on the housing must be checked annually for
dirt. This is necessary so that pressure equalization in the housing can continue, and so
that moisture cannot accumulate in the housing.
3.14 General Information
Burns
Immediately after isolating the device, depending on the operating conditions, certain
components can be very hot (e.g. fuses).
CAUTION!
We recommend that safety gloves be worn during all work on the device.

Parallel Connection of Strings SMA Technologie AG
Page 14 SSM-TEN072310 Technical Description
4 Parallel Connection of Strings
4.1 Maximum Number of Strings per Measurement Input
While the SSM-C is able to connect several strings in parallel, the analysis in the SCC
is, however, limited to a maximum of nine, with a tolerance setting of 10 %. The
maximum number of strings which can be connected in parallel in order to achieve
reliable analysis in the SCC depends on the adjustable tolerance, and can be
determined as follows:
N = maximum number of strings which can be connected in parallel.
The parameter "tolerance" can be adjusted in the SCC.
4.2 Reverse Current
In contrast to the "Sunny Boy" string inverters, in the PV generator of a system using the
Sunny Central, e.g. using thin-film modules, many strings are connected in parallel. The
maximum number of connected strings depends on the module type, and thus must be
requested from the module manufacturer.
Short circuits can cause wrongly directed module current, leading to a string being
subjected to so-called reverse current, which may be considerably higher than the
normal maximum current (short circuit) of the string. Thus, the string fuses protect the
faulty string. The largest permissible string fuse depends on the module type, and must
be selected in accordance with its defined curve.
In principle, reverse current can only occur when modules are connected in parallel
and the open circuit terminal voltage (Voc) of the individual parallel strings is different.
In normal operation, this is avoided adequately when the strings are of the same length.
Since shadowing of the modules has no significant effect on Uoc, even in this situation
no significant reverse current occurs.
In failure-free operation of a correctly dimensioned PV generator, no excessive reverse
current can occur!
Reverse current can only occur due to a fault in the solar generator (e.g. short circuit in
one or more modules) that causes the open circuit terminal voltage of a module string
to be significantly lower than the open circuit terminal voltage of other parallel strings.
N = 0.9 / tolerance (%)
Information
The maximum number of strings which can be connected in parallel is limited
to nine, if the tolerance is set to 10 %.
Thus, if the number of strings connected in parallel is larger than nine, failure
of a string cannot be registered or identified in the SCC.

SMA Technologie AG Parallel Connection of Strings
Technical Description SSM-TEN072310 Page 15
In the worst case, the voltage on the faulty string may lie within the MPP voltage (UMPP)
of the remaining generator elements. The internal diode structure of the solar cells then
causes reverse current to flow through the faulty generator string that, depending on the
amount of current, may lead to excessive heating or destruction of the modules in this
string!
Among other symptoms, the following faults may lead to reduction of the open circuit
terminal voltage of a generator string and subsequent reverse current in parallel-
connected systems:
• Short circuit in one or more modules
• Short circuit in one or more cells in a module
• Double ground fault in a module and/or the cabling
Despite the fact that these faults are very unlikely, and extremely rare in practice,
preventative measures must still be taken. After all, these types of faults carry a high
potential for damage and danger, since all modules in the affected string may be
damaged and the local heating may also cause secondary damage. Thus, it is no
surprise that these issues have long been taken into consideration by the UL
(Underwriters Laboratories Inc.) certifiers in the USA and the reverse current ratings are
a standard specification in US data sheets for PV modules.
On the basis of these potential problems, the SSM-C contains fuses that isolate the
defective strings from the rest of the PV array. When a string fuse is triggered due to a
fault in a module, the software detects this and a warning is generated.
-
+
L
N
Current in the faulty string –
total current of the remaining strings

Structure of the SSM-C SMA Technologie AG
Page 16 SSM-TEN072310 Technical Description
5 Structure of the SSM-C
Depending on the chosen option, the SSM-C can be equipped with a load-
disconnecting switch, and various numbers of string connections. The selection of SSM-
C options or fittings can occur via the option code in the price list. This also defines the
structure and identification of the SSM-C.
The following diagram gives a schematic overview of the various components and
connection points inside the Sunny String Monitor Cabinet with the cover removed:
1 2 3 4 5 6
Z9-X9
L+
L+
Z2-X2
12345678910111213141516
L-
L-
L-
1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8
L+
12
1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8
L-
12
Z1-X1
12345678910111213141516
L+
FA2064706 0002374 Vers.:A1
485HCVBP-01
1131
11/07
FA2064676 0068725 Vers.:C2
2903 06/07
Vers.:A1S/N 1728
SMU8HV-DVPB
Ms60- DC8FS
FA2064706 0002374 Vers.:A1
485HCVBP-01
1131
11/07
FA2064676 0068725 Vers.:C2
2903 06/07
Vers.:A1S/N 1728
SMU8HV-DVPB
Ms60- DC8FS
ABC A BCDE
FGHFIK
JML
D

SMA Technologie AG Structure of the SSM-C
Technical Description SSM-TEN072310 Page 17
Depending on the selected fittings, the interior view of an SSM-C can differ from the
maximum assembly options.
For the connection of RS485 communication, and for the +55 V DC power supply,
terminals are provided in the connection area. In addition, the connection area
provides a contact for the data line's cable shield.
The connection of string lines can be realized by means of the isolation terminals, to
enable load-free disconnection of the individual strings, or all strings, from the solar
generator. String monitoring occurs via the SMU board in the SSM-C, on which a data
processing Piggy-Back (SMU8HV-DVPB) is integrated. The SMU8HV-DVPB realizes the
management of string currents and the SMU board's parameter settings. For connection
of the DC main lines to the inverter, two bolt clamps are integrated within the SSM-C.
The load-disconnecting switch provides the option of disconnecting the SSM-C on the
inverter side. The busbar is necessary for grounded operation, in which the respective
PV pole (negative or positive) is grounded in the inverter. For protection from transient
overvoltages caused by lightning strikes, overvoltage protectors are built into the SSM-
C. A grounding terminal is provided for connection of the equipotential bonding.
A Communication Piggy-Back
B Jumper for communication
C Data processing Piggy-Back
D LEDs for display of operating mode
EDCswitch
FDCfuses
G Communication socket
H DC string connections: + pole
I DC main line: + pole
J Ground connection
K Overvoltage protectors
L DC string connections: - pole
M DC main line: - pole