NETWORK LOAD STRESS TEST FOR SMART SUBSTATION

In Smart substation, community of secondary device from 3 layers, named substation layer, bay layer and procedure layer, consists of networks, substation network and system network. The former makes use of IEC61850-8-1 protocol, in different words MMS(Manufacturing Message Specification, MMS)protocol to conversation with every different, and the later adopts multicast registration protocol to transmit SV- (Sampled Value, SV) and GOOSE(Generic Object Oriented Event, GOOSE) messages. In IEC61850 standard, electric powered quantities, which includes voltage and modern-day are transmitted via SV messages, and position alerts of switches, trip/close alerts, manipulate signals and interlocking alerts are transmitted thru GOOSE messages. Compared to traditional substation, smart substation together with community secondary gadget is most associated with network, relays, dimension and con-trol devices may additionally be mal-operated caused by wrong facts move in case of substation layer or system layer community failure[7]. At present, network of secondary gadget must be tested cautiously under everyday and unusual condition, and consi-dered as having the identical position as relays and different automation devices in clever substation. Network load stress check is a normal test object for communication, information network as following:

(1) with the aid of gradually increasing the network load, the most load performance of the community can be determined.

(2) by means of gradually growing the community load, the community failure kingdom and the corresponding maximum load may be de-termined.

Network overall performance take a look at, particularly load stress test of secondary system community are critical for the large-scale construction of smart substations. General imported network check device on the market commonly output IP messages, inclusive of TCP, UDP, ARP, etc. In load stress check, the above messages are one of a kind from facts circulate in clever substation and aren’t very appropriate for community take a look at in clever substation. Several secondary system network sch- emes and their impact on relays related IEDs are discussed, after which stress take a look at objects, functions, ideas for smart sub- stations are proposed. Based on embedded CPU and large- scale FPGA, a brand new load stress check device for secondary equipment network in clever substation is applied with function of supplying multi-type stress facts circulation together with IEDs’ necessary working stream, and field check exercise is introduced within the end.

SCHEME OF SECONDARY EQUIMENT NETWORK

Secondary gadget network includes substation layer network and process layer community, scheme of the former one is tremendously fixed, and the later one usually is composed double networks named A and B community corresponding to double configured relay A and relay B in smart substations of 220kV or better voltage, and meters are linked to process layer community A, while size and control gadgets, fault rEcorders, network recording and analysis devices are related to each the double technique layer networks. There are several schemes of process layer community, interfaces and communique scenario of devices vary from extraordinary schemes. Because area limited, handiest the affect of schemes of technique layer community on IEDs(Intelligent Electric Device, IED) relative to relays are discussed in this paper. The manner layer network may be categorized to the following three traditional schemes in terms of S-V, GOOSE connection to relays.

DIRECT CONNECT SCHEME

Network diagram of smart substation of 220kV with direct-connect scheme is depicted in Fig.1. Relays get SV and GOOSE messages through connecting to MUs(Merging Unit, MU) and STs(Smart Terminal, ST) point to factor, at the same time as other gadgets like meters, fault recorders, community recording and analyzers acquire SV and GOOSE messages thru process layer network. Anticipated goal of the scheme is that behavior of relays is totally independent of the network. However, interlocking signals go bays are transmitted thru network between relays, as the dotted strains shown in Fig.2. For example, bus relay transfers remote tripping, blockading reclosure signals to line relay via the manner community switch, and line relay sends trigging failure signal to bus relay the same manner as proven in following figure. There are signals transmitted thru network even in one bay, such as function indicators of disconnectors are despatched by clever terminal to line MU for bus voltage switching thru the community switch.

Merging Unit: take the line MU as an example, it has ma- ny conversation ports, such as direct-connect SV output ports, community SV output ports, cascaded input SV ports, community GOOSE enter ports and community GOOSE output ports for display its wholesome and operation state. As a long way because the reliability of MU is concerned, the impact of every port’s load on different ports have to be properly designed and tested.

• The effect of data circulate of cascaded SV input ports on different MU ports, such as direct-connect SV output ports, network SV output ports, community GOOSE ports, etc.

• The impact of statistics flow of network GOOSE ports on other MU ports, along with direct-join SV output ports, network SV output ports.

• The impact of statistics circulate of community SV outputs ports on direct-join SV output ports, community GOOSE ports.

Smart Terminal: smart terminal of line bay with direct- connect scheme has the subsequent ports, line relay direct- join GOOSE port, bus relay direct-connect GOOSE port, and lots of community GOOSE ports, and the impact of each port’s load or information circulate on different ports need to be nicely designed and considered.

• The impact of statistics stream of direct-connect GOOSE ports on other direct-join GOOSE ports, network GOOSE ports.

The impact of records move of network GOOSE ports on direct-join GOOSE portsand other network GOOSE ports.

Relay: line relay has one factor-to-point SV enter port with direct-connect scheme as proven in Fig.2, whilst transformer and bus relay have greater direct-join SV input ports. Also, line relay configures direct-join GOOSE port for line smart terminal, community GOOSE port for bus relay and MMS port for conversation with substation layer devices. In the equal way, the impact relation of every port’s load or data stream on other ports is listed below.

• The effect of information movement of direct-join SV enter ports on other direct-join SV enter ports, direct- join GOOSE ports, community GOOSE ports, and the MMS port.

• The effect of records flow of direct-connect GOOSE ports on direct-connect SV input ports, community GOOSE ports, and the MMS port.

• The impact of information move of network GOOSE ports on direct-connect SV enter ports, direct-connect GOOSE ports, and the MMS port.

The effect of data stream of the MMS port on direct- join SV enter ports, direct-join GOOSE ports, and network GOOSE ports.

SEPARATE NETWORK SCHEME

Secondary device community diagram of clever substation with separate network scheme is depicted in Fig.3. There are separate SV and GOOSE networks, and MUs connect to each the SV community and GOOSE network, STs handiest connect to GOOSE network. With this scheme, relays, size and control devices, meters, fault recorders, get SV and GOOSE messages through networks.

Compared to direct-join scheme, there are much less com- munication ports of IEDs with separate network scheme, however, SV and GOOSE ports traffic of relay increase and smart terminal tripping and last digital circuits are connected to network inside the risk of tripping/reclosure failure caused by network. Relays associated IEDs inclusive of relays, MUs, STs are most related to community, the impact of network load on IEDs’ functions, performance must be evaluated carefully, and the equal for the affect of community ports on each other.

COMBINED NETWORK SCHEME

Secondary system community diagram of clever substation with combined network scheme is depicted in Fig.4. MUs, STs, Relays are linked to the same system layer community, SV and GOOSE messages are shared by devices a few of the network. In smart substation the use of IEEE1588 PTP, IEEE1588 PTP messages are also transferred through the same network with SV and GOOSE messages, which is likewise named three net- works merging scheme. Compared to the above direct-connect scheme and separate community scheme, there are much less conversation ports for MUs, STs, Relays, however a good deal SV and GOOSE ports traffic of relays. The virtual local vicinity network(VLAN) generation is used to balance the manner layer network site visitors, lower the community congestion and optimize the network performance.

With the combined community scheme, relays greatly rely upon network, the impact of community load on IEDs’ functions, performance ought to be considered and evaluated.

PRINCIPLES OF NETWORK LOAD TEST

In smart substations, communique ports of IEDs may be categorised into 5 types: SV input ports, SV output ports, GOOSE input ports, GOOSE output ports, MMS ports if IED linked to substation layer network, SV or GOOSE ports may include direct-join or community ports.

According to the enterprise widespread of SGCC(State Grid Corporation of China, SGCC) Q/GDW 441-2010 Technical specs of safety for clever substation, the require- ments about IEDs communication ports and networks for clever substation are listed below.

• Smart substations of 220kV or higher voltage must configure double relay protections and corresponding double procedure layer network, and the technique layer networks are unbiased from every other.

• SV community, GOOSE community, and MMS community of smart substations of 110kV or better voltage must be independent from every different, and relays should connect with every network through impartial facts interfaces.

• Fault recorders, community recording and analyzers ought to connect with SV, GOOSE, MMS community through unbiased facts interfaces.

Data interfaces range from IEDs, general ports version of IED. Network load effect path between ports is depicted as dotted lines inside the figure

Principles of network load pressure check are listed underneath in accordance the above standard specs and network test exercise for smart substations.

• Network load pressure check can be done in two styles: community environment test and character IED check, the former can be completed for the complete community to determine the most load pressure corresponding to network or IEDs failure a few of the net- work, and the later for man or woman IEDs.

• With network environment check, the community under take a look at should no longer have an effect on other networks and IEDs . For exam- ple, substation layer community load pressure check should now not bring about abnormalities of system layer community and IEDs. As for IEDs connect both the method layer community and substation layer community, inclusive of relays, substation layer community load stress take a look at should not bring about abnormal conduct and ports performance corresponding to procedure layer community.

• With man or woman IED check, load stress of ports under check should now not affect the receiving, sending, and information processing of other ports.

• IED system layer non-subscription port messages stress should no longer affect IED performance, function, and data sending, receiving, and processing of different ports when general load traffic of that port is under port’s maximum designed traffic. Non-subscription port messages refers to messages unexpected acquired by way of that port, along with IP messages, random messages, broadcast messages, and different messages simplest subscribed via different IEDs.

• IED technique layer subscribed port messages stress should no longer have an effect on different records circulate sending, receiving, and processing when overall port load site visitors is under port’s most designed traffic. Subscribed port messages refers to messages anticipated received via that port, meanwhile, both the MAC cope with and APPID code in messages are correct.

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