First thing we should say is that it is almost impossible to introduce something new in such type of device. But one may develop such a product that is reliable and of the great usability. SICAM IO, as we found out, is one of such products. The enclosure of the product is made of good quality plastic (feels like you should not be scared if it falls down) and has DIN-rail mounting mechanism (which also seems to be a reliable one).
According to the manual there are different models of this product: number of binary inputs/outputs may vary, IED may come with different interfaces, it may have integrated switch function, etc. We had a device that was equipped with maximum possible options: with 6 binary inputs, 6 binary outputs, IEC 61850 support and integrated switch function.
Functions of the device are quite limited. This means that it cannot perform any other functions besides its main one: to convert 6 status signals, received through one or 6 different GOOSE-messages, into operation of one of the available output relays. Or: to publish single GOOSE-message with 6 status signals. Yes, there will be only one GOOSE-message with 6 status signals. Mentioned data can also be transferred with Report service (MMS).
We thought that device lacks the possibility of logic charts creation: few AND, OR gates plus a timer could turn this IO unit in a very interesting stand-alone solution. But then it would be an absolutely different device. If to speak about useful functions – it’s worth mentioning integrated switch function, which we will discuss further.
Configuration of the device (besides GOOSE-subscription which will be discussed further) is carried out using web-interface, which we found to be pretty straightforward and easy. There you can set almost everything: starting from IP address up to binary inputs operation thresholds and filtering time.
Regarding IP address it is worth saying some additional words. We think that almost everyone had the problem accessing the device, which IP address is not known/forgotten/lost. It is not a problem for devices equipped with either serial of USB interface which can be used to access configuration data. If there is only Ethernet interface available then to access the device one uses a special utility (vendor-dependent network discovery tool). In reality this tool is not so easy from technical point of view because to access any device in the network it should use some native Layer 2 protocol. This means that it should directly interact with network controller – not through socket interface as during IP communication. That’s why in practice problems arise. Based on our practical experience we should say that these utilities do not always work properly. This lyrical digression was made just because we think that there is rather reasonable solution for this problem in SICAM IO. There’s “IP-Addr.” button available which makes it possible to set default IP address temporarily. Key word here is temporarily. During this time period one will be able to access device configuration through web-interface and check IP address that was set previously. If no changes to IP address during that session were made then then after logout device will set the IP that is there in configuration settings – the one you could not remember/find earlier. So you will have no problems accessing the device further.
As it has already been mentioned, during configuration process user can set binary input operation threshold in Volts plus it is also possible to set filtering time at binary inputs (chatter blocking).
For binary outputs there us a possibility to set signals assigned to them. There are following possibilities:
- External signal, received in digital form (through GOOSE message).
- Signal from binary input.
- Signal from the internal logic of the device (communications failure, diagnostics, etc.).
For each of 6 available outputs it’s possible to select the needed signal from drop down list.
IED information model is very easy and includes 6 logical nodes:
- LN0 – system logical node.
- LPHD – logical node for representation of the state of the physical device.
- ZBAT – logical node to represent the state of the internal battery (provide internal memory power supply at auxiliary power supply loss).
- InGGIO1 – binary inputs status signals. Logical node includes 6 data objects (which correspond to available inputs).
- ProxyGGIO1 – logical node for mapping of external signals, received through GOOSE-messages. It includes 6 data-objects, to which user can assign external signals.
- OutGGIO1 – binary outputs status signals. This logical node includes 6 data object with each of them represents the status for the corresponding binary output.
There are two fixed data sets available: one includes signals from logical node lnGGIO1 (DA_Inputs) and another includes signals from logical node OutGGIO1 (DA_Outputs). There are also two fixed GOOSE control blocks, referencing corresponding data sets mentioned earlier. Plus user may find two buffered reporting control blocks – again referencing mentioned data sets.
All the configuration is fixed except for GOOSE subscription part. It’s worth saying though that there’s no real need to have everything configurable.
Finally we got to the most interesting part – ability to perform to GOOSE messages from external device in DIGSI. User can simply add SICAM IO unit in IEC 61850 station in DIGSI as a communicator. This is done in a regular way as you are working with SIPROTEC IEDs. Though there are a few nuances to point out:
- Final configuration is loaded into SICAM IO not through SCD file but through a special binary file that you will have to create in custom application. This operation is performed in two steps: one has to choose Load SCD option and then Generate configuration option. This binary file Is then loaded into device through web-interface.
- You have to be attentive when it comes to IED name attribute that is there in SCL file. This parameter must have the value of S_IO_xxxxx. SCL file with IED name attribute of this and only this value will be accepted by custom application for binary files creation.
Generally we should say that convenience of configuration process may be qualified as good. But this is only the case if you had experience of working with DIGSI. Otherwise you will understand why we added this condition.
Integrated switch function
When we speak about IED and say that it has integrated switch inside we usually expect to see minimum two Ethernet ports on it. But in this case it’s different – absolutely different. Having received this SICAM IO with one Ethernet port we were like: “Okay, what have you sent to us? We asked for the model with integrated switch”. But having checked order code we found that the device has order code of a model with switch inside. We decided to study the manual (do you also read manual afterwards, don’t you?). It was there… switch was inside. But not a common one. Of course IT guys know that in 100Base-TX networks only 2 of 4 couples of wires present in UTP/STP cable are used. This IO can use all 4 and implement data exchange using totally 8 wires. So if you make splitter you get a switch. According to the manual there’s a special cable to use this integrated switch function – it is called Y-cable. One can buy it – Siemens can supply it and there’s even an order code for it. But we made it by ourselves. It took some time to find the Y-splitter schema on the Internet though. Then using bridge connector we made it and you can see it in the picture below. Although it doesn’t look like series product (sorry!!!), it worked fine.
Now it’s time to tell what this integrated switch allows you to do. First let’s imagine the following case: we are doing the design of protection and automation system for the enclosed switchgear. In SIPROTEC COMPACT that we decided to use we lack binary inputs. Typical case: we decided to save some money and not to use SIPROTEC 4. Instead we introduced SICAM IO. We did the design but finally forgotten about Ethernet switch – it may lack ports. Here comes SICAM IO integrated switch function: you can connect end device through IO unit using Y-connector. Such solution works if end device is connected to the network through electrical Ethernet interface.
Of course it is of our intention for this end device to transmit important GOOSE-messages (not only for implementation of interlocking function) so it’s of importance for us that IO is not introducing any communication delays. To check this we created a simple test setup with the usage of RETOM-51 (Russian analog for OMICRON CMC356). RETOM was used in a timer mode. It generated binary signal which was transmitted at protection IED1 input. Then IED1 generates GOOSE-message with a status value of its binary input. IED2 is subscribed to this message. The signal introduced by this GOOSE-message is mapped to the IED2 binary output. The operation of IED2 output relay is recognized by RETOM.
Test were performed for two cases:
- IED1 is connected to the external Ethernet switch directly (see pic. A).
- IED1 is connected to the external Ethernet switch through SICAM IO using Y-cable (see pic. B). It may not be clear on the pic but the common end of Y-cable is connected to SICAM IO.
We performed 10 tests for each case. As we are not into convincing anyone here so we will just present two sets of the results here:
CASE A — DIRECT CONNECTION
Тmin =0,0095 s
number of triggers=10
CASE B — CONNECTION THROUGH SICAM IO
Тmin =0,0096 s
number of triggers=10
Results we got show that SICAM IO and its integrated switch function can be used in those cases when end device is connected through IO – the transfer time of the GOOSE-message is comparable to the case when end device is directly connected to external Ethernet switch.
We also tested SICAM IO for GOOSE-perfomance using ping-pong method and may say that its performance is one of the best we have ever seen.
We tested yet simple but quality product. Its functions are in accordance with declarations and IED is implemented with German thoroughness. Don’t take this as an advertisement of the product but this IO does the job right way.
We didn’t consider prices for this product because this column is devoted to consideration of technical questions only. Let somebody else check the price.