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What's App:+86 139 0307 8125 E-mail:repsun1@xierli.com
Abstract: Manufacturers of SPDs understand that their devices will
eventually reach an end-of-life state, whether due to natural aging or due to
conditions being imposed which are outside of normal operating conditions.
International standards bodies such as the Electro Technical Commission (IEC) and Underwriters Laboratories Incorporated (UL) recognized the hazard posed by a failed SPD and include a number of tests in standards such as IEC 61643-12, IEC 62305-4 and UL 1449, to ensure that such devices fail in a safe manner. In order to comply with such standards, SPD manufacturers rely on “disconnectors”. This paper introduces the importance of SPD “disconnectors” to the safe installation of an SPD and expands on aspects such as,internal versus external disconnectors and over-current versus thermal disconnectors. It also details the current methods used to evaluate the behaviour of disconnectors by these various standards setting bodies and the steps being taken to improve on these in new draft editions under development.
An SPD by
definition contains at least one nonlinear component which is intended to limit
the surge voltage and divert the surge current. Inherent in the operation of
such devices is the possibility of unexpected failure or rapid end
of-life. Under such conditions, it is important that the SPD can safely isolate
itself from the prospective supply to which it is connected without presenting
a potential fire hazard.For this purpose a disconnector is usually
incorporated,either in the housing of the SPD itself (internal disconnector),
or as a separate component installed in the electrical network up-stream of the
SPD (external disconnector).
The
importance of such disconnectors to the safe operation of an SPD can not
be over emphasized. It is for this reason that manufacturers put so much
engineering effort into the careful design of disconnectors and standards
committees,such as UL 1449 and IEC 61643-1 , into the testing and
evaluation of such devices.
A well
designed SPD, or SPD installation, will generally require one or more
disconnectors for safe isolation from the prospective current of the energizing
supply during fault conditions. Without such, it is a potential fire hazard or
explosion waiting to happen.
The
failure mechanism of an SPD can generally be categorised as:
§ A gradual end-of-life due to natural degradation (ageing) of the internal non-linear component(s) during normal operation, or
§ A rapid
end-of-life due to a catastrophic event outside the scope of the SPD’s normal
range of operation.
These two
scenarios, by which an SPD can reach its end-of life, generally place very
different requirements on the disconnector(s).
Thermal
disconnector - In the first case, where the failure is associated with a
gradual degradation of the internal non linear components (metal oxide
varistors), a disconnector which is capable of sensing the thermal rise in
temperature of the SPD is generally required. The objective being to isolate
the failing varistor before it reaches thermal runaway and becomes a fire
hazard.
Gradual
degradation of the SPD can result from many causes, but most common amongst
these are:
§ Ageing
of the metal oxide varistor (MOV).
§ Sustained
temporary overvoltages (TOV) of the power system, either due to poor system
regulation (as in the case of long transmission lines), or when a
multiphase system becomes unbalanced (as in the case of a loose neutral
connection on US 120/240V systems).
Under such conditions, the rms current conducted by the SPD is usually limited to a few tens of amperes as it starts to enter conduction on the peaks of the sinusoidal supply, resulting in a progressive and gradual rise in temperature.
Over-current disconnector - In the case of the very rapid end-of-life (which can occur when an SPD is exposed to unanticipated events such as - a surge beyond its intended rating, or a large TOV as can occur when there is comingling of the HV and LV system) the disconnector must operate extremely fast in order to limit the energy of the prospective short-circuit current available from the supply to which it is connected. Under such conditions, a thermal disconnector would operate too slowly and the energy created in the failed SPD could result in a catastrophic explosion of the housing, and fire due to mains follow-current.
To prevent this, an “over-current disconnector” such as a fast acting fuse or magnetic circuit breaker with well coordinated I2t characteristic, is required. This need to include fast operating over-current disconnectors, has also meant that manufacturers need to grapple with a trade-off between fast isolation (high SCCR rating) and a low Imax (low maximum discharge current).
DC current disconnector – The growing interest in renewable energy generation has lead to a proliferation of photovoltaic panels in applications ranging from small residential installations to large commercial “sun farms”.Such installations by their very nature are externally located and thus particularly subject to the effects of lightning induced damage. As a result, the use of SPDs on such panels is becoming increasing important and new standards are being developed to address the testing and performance of SPDs intended for use on DC power systems. The disconnector in a DC-SPD needs to be designed in a very different way to that used in an AC-SPD. Not only does it often have to isolate much higher voltages (photovoltaic systems typically operate at 300, 600, 1000 VDC), but it also has to disconnect (open) when there is no zero crossing point to extinguish an arc as there would be on an AC system.
SPD
manufacturers are only just starting to address these more onerous
requirements. A number of innovative new disconnection designs have been developed
and patented.
Most of
these use various mechanical shutters to extend the arc length while
disconnecting, thereby cause self extinguishing even though a voltage
zero-crossing point is not present.
Surge Protection for Energy Storage Systems(ESS)
Energy Storage Systems (ESS) are now a mature technology. ESS is installed at sites to improve energy management control such as peak management or frequency regulation, or for renewable energy storage for photovoltaic or wind generated energy applications. The importance of such equipment makes interruption of their service unacceptable, so measures must be taken to limit damage due to external influences. One of the risks to be taken into account is possible damage due to transient overvoltages generated by lightning or by switching operations.
The deployment of ESS has demonstrated the limited robustness of these equipments, including batteries systems. Specialists in this technology have ascertained that their low impulse voltage withstand (Uw) may lead to critical system failure.
Surge Protector for ESS
Surge Protection Device (SPD) technology is widely used in AC power networks to protect equipment connected to them against transient overvoltages. Test standards (IEC61643-11), and selection and installation guides (IEC61643-12, IEC60364-5-534) have been in existance for many years, they define reliable products as well as their selection and implementation. However, regarding DC power networks, neither standardization is available at the time of writing (late 2020). In fact, the standards for surge protection for DC power are ongoing at international level (IEC) such as the following standards:
This standard IEC61643-31 is extrapolated from existing standards of surge protection devices for AC networks (IEC61643-11) and the sizing parameters (In, Uc, Imax, Up…) and test procedures is similar because they will be grouped in a new document common to the two documents.
The IEC 61643 series is moving toward a new philosophy. A new document (IEC61643-01) will gather all the definitions and tests common to the various applications of SPDs (AC power, PV power, Dataline, DC power) and the dedicated standards ( IEC61643-11, IEC6163-21, IEC61643-31, and coming IEC61643-41) will focus only on the specific tests for the application.
Regarding safety tests that simulate the end of life of the SPD such as thermal runaway or short circuit behavior, the procedures are therefore similar as well as the necessary means to achieve requirements, namely the use of internal disconnectors to withstand the thermal runaway tests, and associated fuses to withstand short-circuit tests.
The need to protect ESS equipement against transient over-voltages
Specialists in ESS equipment have noted a reduced robustness in impulse overvoltage of these equipments – particularly in battery systems – and due to the imperative need for continuity of service they recommend the use of surge protectors at their terminals. Surge protection on the AC part is also recommended. For the following reasons and consequences, the critical point is the protection of the battery storage system. When the maximum DC operating voltage is very high (1000 Vdc and more), in such cases a specific SPD is necessary, it being compatible with these voltages and in conformity with the future IEC61643-41. In cases of potentially extremely high short circuit current (100kA and more), the surge protector must withstand the short-circuit test being associated with a fuse sized accordingly.
To manage the short-circuit test, it is imperative that the surge protector is used with an external fuse. The fuse must be rated high enough to conduct 5kA at 8/20μs impulse current without opening, but rated low enough to protect the surge protector during its failure on the short-circuit test. Regarding the breaking capacity, this is the likely short circuit current calculated at the time of installation. Provided by the surge protection manufacturer, these requirements can make fuse rating selection somewhat difficult in the case of very high power DC installations.
Use of the existing upstream fuse
It could be considered to use the existing AC power SPD overload protection fuse upstream as protection of the SPD. This is only possible if its rating is equal to or less than the value declared by the manufacturer of the SPD. For high power installations, the fuses have very high ratings, making this option a non-starter.
ESS surge protector selection
In conclusion, the key criteria for the selection of DC SPDs, extrapolated from AC standards is:
* Type 2 Surge Protector (no proven risk of direct lightning discharge)
* Uc (max. operating voltage) is greater than Umax of the DC network + 10%
* In (Nominal discharge current) is greater than 5kA
* Isccr (admissible short-circuit current) with associated fuse is greater than Icc at the installation point.
(source: pewholesaler.co.uk by Switchtec Ltd)
To mitigate the effects of transient overvoltages, Surge Protective Devices (SPDs) are used throughout electrical distribution systems, such as at service entrances, transfer switches, and downstream panelboards. Manufacturers state surge capacity ratings as either Per Mode or Per Phase. This paper describes how these terms apply to SPDs used in three-phase, four-wire Wye systems.
SPD Modes Defined
In the context of SPDs, the term mode refers to the types of pathways available for shunting overvoltages. These pathways are most commonly formed by bridging two conductors through a Metal Oxide Varistor (MOV). These components are non-conductive at nominal circuit voltages, but become conductive when higher voltages are present. When that occurs, the varistor shunts excess voltage from the conductor of higher potential to the conductor of lower potential.
In a three-phase four-wire systems, four pathways are possible:
• Line-to-Neutral
• Line-to-Ground
• Neutral-to-Ground
• Line-to-Line
Each is shown in Figure 1.
Many three-phase applications use SPDs that offer complete line-to-neutral, line-to-ground, and neutral-to ground pathways, for a total of seven modes of protection. This arrangement is shown in Figure 2. SPDs that also provide line-to-line pathways offer 10 modes of protection. This brief will use seven-mode SPDs in subsequent examples.
Per Mode Rating Defined
An SPD’s per mode rating is based on the total amount of energy it can shunt from one circuit conductor to another. If an MOV capable of shunting a 50 kA of current is used in each pathway, then the per mode rating of the SPD in Figure 3 is 50kA.
If multiple MOVs are used between the same conductors, then the per mode rating will be the sum of the capacity of the MOV’s used in these pathways. Figure 4 shows a seven-mode SPD with three 50 kA MOVs installed between each pair of conductors. The per mode rating of this MOV is 150kA.
Per Phase Rating Defined
A different way to rate an SPD is to state the total capacity of the protective components serving each of the three phase conductors. Using the same seven-mode SPD with 50 kA MOVs, Phases A, B, and C are each served by two MOVs (one to neutral, one to ground). The per phase rating for the same SPD is 100 kA, as shown in Figure 5 below. Applying the same rating scheme to the SPD in Figure 4 above produces a per phase rating of 300 kA because each phase conductor is served by six 50 kA MOVs.
1.1: The technology of REPSUN lightning rod:
The latest technology based on early streamer emission.
1.2: The technology of conventional lightning rod:
Around 260 years old design based on Franklin technology.
2.1: Work principle of REPSUN lightning rod
A. The ionization device is charged via the lower electrodes using the ambient electrical filed (several million volts/meter when storms are prevalent). This means REPSUN ESE lightning rod system is a fully autonomous system requiring no external power supply.
B. The ionization phenomenon is controlled by a device which detects the appearance of a downward leader, the local electrical field increases rapidly when a discharge is imminent. REPSUN ESE lightning rod detects charges in the field, making it the first ESE air terminal to react at the precise moment when the downward leader develops from the cloud to the ground.
C. Early triggering of the upward leader using a system of spark ionization between the upper electrodes and the central tip. REPSUN ESE lightning rod’s ability is to trigger an upward leader ahead of any other protruding point in the protected area ensures it will be the preferential point of impact for the lightning discharge.
2.2 Work principle of conventional rod.
Depends on naturally occurring corona and hence the huge current flows through the rods and the down conductors which results inside flashes and earth potential rise (i.e. the rod will always wait for lightning flash to fall on the tip of rod). In case the factories naturally produce charges like chemicals and metals which may attract the lightning current on its metal parts. At this time, the metal part which is emitting charges becomes more active than the lightning rod which is inactive & lightning current will hit on the metal part rather than hitting the lightning rod.
3.1 Protection radius of REPSUN ESE lightning rod VS conventional lightning rod
REPSUN ESE lightning rod: Wider protection radius according to the standard NFC17-102:2011
3.2 Conventional lightning rod: Limit protection radius
REPSUN offer user name and passwords to login REPSUN smart online monitoring website like below:
Valid code should be all lowercase.
1.How to insert the SIM card in the Smart GSM host?
First of all, we can see the diagram next to the SIM card port, according to the diagram prompt: put the correct direction of the card, and then insert in.
2.How to take out the SIM card from the Smart GSM host?
First, we need to find a little pointed things (for example, return needle / nib, etc.), and then use it to press the SIM card, and it will automatically pop up.
3.How to connect the resistor to the Smart GSM host for resistance value test?
Find suitable resistors prior to testing, note that the resistance value range of our product is (0.01-500 Ω).Also ensure that the PC and E ends are well connected.
Why we need to test it with a resistor is designed to verify the accuracy of our products.
4.How many models of Smart GSM have?
Three types:
REP-GSM16 is loop method;
REP-GSM26 is leakage current;
REP-GSM36 is 3-point test.
5.How to modify the model on Smart GSM host to "GSM36 001"?
①.Please kindly change it to "Type: GSM36 001" then press the MENU button and UP button to change it
②.Then 001,also need press the MENU button to save it
③."Thr " also need to press the MENU button
④."Vol Thr" also need to press the MENU button
⑤.Finally press the "ESC"button if you finish above step,need to restart the Smart GSM then check again the "Type:GSM36 001" is okay.
6.How to test the resistance value of the Smart GSM?
Smart GSM Testing: Before Smart GSM testing need to make sure the Grounding Resistance Monitor Status is ON.
We can follow this step to check it:
①.Press 1 time MENU Button,and find the “Sys. Set.(System setup)”then press again the MENU Button.
②.When you enter into the “Sys. Set.(System setup)”,you need to find the "Res.Module(Grounding resistance module)" press again the MENU Button.
③.When you enter into the "Res.Module(Grounding resistance module)",you need to find "Res.Monitor(Grounding resistance Monitor)"
④.Check the "Res.Monitor(Grounding resistance Monitor)" is on.
Make sure the "Res.Monitor(Grounding resistance Monitor)" is on,then we can start to test the Smart GSM.
WAY 1: Website to click the "Test" then waiting the data coming.
WAY 2: Also can press 4 times the DOWN button,then 1 time for the MENU button.(Requires continuous and consistent pressing.)
7.How to modify the information on the web page version?
Need to modify：F.M.Mon.(Remote signal monitoring)
①.Press the "MENU" button find the Sys. Set.(System setup)then press again the "MENU" button enter into new page.
②.Find the "F.M.Mon.(Remote signal monitoring)then press the "MENU" button enter into new page.
③.Press again the "MENU" button and press "UP" button to change the "ON" to "OFF"
④.Press the "MENU" button to save the setting.
An SPD providing monitoring of its environment and communication capability (either locally or remotely) to provide status of the SPD as well as lifetime expectancy and possibly other functions such as surge intensity, surge counter, surge time, leakage current, grounding resistance, grounding wire connectivity, temperature and humidity, etc.
Smart implies two things: Interaction with other devices based on faraway communication (internet of things), and when possibly a tape of analysis (to inform a user that is SPD has failed in nice, but why it has failed is smarter).
Smart SPDs usually includes three functions: Surge protection, monitoring and communication.
Monitoring function of SPD operation status & parameters detecting; can match with communication interface & data remote transmission.
Due to the fact that most of our SPDs have plastic housing and parts, in the event of SPD short-circuited or overloaded, large amount of heat will be dissipated, the plastic housing or parts might become distorted, this might prevent the releasing mechanism to operate as SPD original design, and fail to disconnect from the main power. Therefore for double safety reason, additionally at the power SPD upstream we also installed a fuse or circuit breaker.
But REPSUN SPD doesn’t require fuse or CB as there is a back-up fuse in REPSUN SPD already for double safety.
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