A smart grid is a utility grid that uses an Ethernet communications network to link various remote sites and control rooms into a single logical entity. This network architecture can then be used automatically and remotely to gather and act on information.
Moving over to a smart grid solution can be a daunting task, especially to someone who is not familiar with the working of Ethernet. However, if tackled on a piece by piece basis, a smart grid system is not overly complicated, and the time and expenditure savings provided by a smart grid far outweigh the time, planning and expenditure needed to deploy the communications network.
Hardware
The first topic that needs to be addressed when planning for a smart grid system is the hardware that will make up the communications infrastructure, of which two aspects must be addressed. The first aspect of the hardware that needs to be looked at is the physical capabilities and tolerances the hardware provides. As this hardware is going to make up a highly critical communications network, it needs to be rugged enough to handle the harsh environments that can be found in the utility world. Substations are often located in highly remote areas that can experience extreme temperatures, with the mercury climbing during the day and plummeting at night. These areas are also often dusty, humid or similar, and can contain high amounts of EMI (electro magnetic interference), especially the MV and HV environments.
Hardware is available that caters for all these environmental hazards, and must be carefully selected to give the peace of mind that you are running a strong, stable network. Often manufacturers will offer a conformal coating option, where the PCBs of the units are coated in a thin silicon layer, meaning dust and moisture cannot come into direct contact with the circuitry. Ethernet vendors in the utility world will often offer EMI resistant/immune hardware, and by using fibre optic cabling rather than copper cabling the effect of EMI can be reduced (as fibre optic cable is not affected by EMI).
The second aspect of the hardware that needs to be taken into account is the logical aspect, in other words the protocol support and functionality the hardware provides. Smart grids will generally separate the network traffic using VLANs, which puts much less load on the end devices. Also redundancy is a big concern, as one cannot allow a single cable break to pull down a whole section of the network. All this functionality is provided by the Ethernet standard, however many manufacturers also offer their own proprietary mechanisms, especially for redundancy.
It is recommended to rather use open standards where possible, as this prevents the user from getting locked into a single vendor’s products. The IEEE (Institute of Electrical and Electronics Engineers) has standardised many of the Ethernet mechanisms available, and if a vendor’s device complies with a part of the standard it means that hardware will be compatible with other vendors that comply with that part of the standard. For instance, any device complying with IEEE802.1Q (VLANs) will be interoperable with any other device complying with the same standard, and will be able to understand the VLAN packets sent from those devices.
Security and access control
Another highly important aspect that must be addressed is the security of the system. A smart grid is a highly critical system and any malicious access can be devastating. Security can also be broken down into physical and logical aspects, both of which will play their own role in protecting the system and the grid.
Physical security involves gaining physical access to a device. Many Ethernet devices will cater for a ‘backdoor’ serial port, which can bypass many of the logical security aspects of a network (authentication, firewalls etc.) If a user with malicious intent manages to get direct access to a device, they can cause havoc on the grid by changing the configuration of the device or even just by physically changing/removing connections or power.
Physical security must be in place to prevent this type of access. Fortunately, the communications network greatly facilitates security and access control, as a central control room can overwatch many remote sites. Using IP video solutions administrators can get a visual of who wants to gain access to a site, and can control gate locks remotely if required. Biometrics can also be all linked to a central control room, allowing for easy administration and maintenance. Being able to quickly add or remove a user from the ACL (access control list) remotely means that time is not wasted sending an authorised administrator out to the remote site just to change the ACL.
Logical security relates to the access granted to users who connect to the network, whether locally or from an outside interface (such as any Internet connections or public clouds). Many mechanisms exist within Ethernet already to address this side of security, such as using firewalls to protect against any outside intrusion or to split corporate network sections from the production network sections. Using a SAM (secure access management) solution also provides a larger degree of control over which user can access which devices.
A SAM works by assigning each user a personal username and password for authentication to the SAM server. Once authenticated to this central server, the users will be presented with a list of devices they are permitted to access, without being made aware of the IP addresses, passwords etc. of the devices. If they wish to log into an end device, they will select it from the list presented to them by the SAM. The SAM will then handle the authentication to the end device, so the username and password will remain transparent to the user.
A SAM solution also provides further control, such as the ability to fully track end user’s activities, alerting administrators to unauthorised access attempts and even the ability to limit the access of a user once they have logged into a device (For instance some users may only need read access while others require full read/write access to a device). Some SAM solutions will even offer additional modules that can be installed, providing functionality such as automated configuration and firmware management.
Data concentrators and serial device servers
When upgrading a legacy grid to a smart grid solution, it can become extremely costly if every device on the network needs to be replaced with a newer device to provide Ethernet capabilities. Components are available that will ease this transition, and allow users to maintain their investment in legacy devices while still gaining the benefits provided by a smart grid.
The first of these is a Serial Device Server, which is a device that can package serial data directly into Ethernet frames for transmission over the Ethernet network. On the other side one can either use a second serial device server to 'unpack' the data and push in out as the original serial stream, or alternatively one can use a software package that creates a virtual serial port on a PC. This software can receive the Ethernet packed serial data and unpack it, then forward the serial data on to a software application. Using serial device servers, one can extend a serial connection anywhere over the Ethernet network in a manner that is completely transparent to the end devices (i.e. the end devices will believe they are connected by a point to point serial link.
A second component that can be used is a data concentrator, which in its base form acts as a translator between various different protocols. This is especially important when integrating legacy devices, as many different forms of serial and IP communication exist. Using a data concentrator, one can take various different protocols and translate them into a single master protocol for sending on to a central control centre, or can translate between the different protocols for interoperability between end devices. Once again, the savings and benefits that a data concentrator solution can provide far outweigh the initial cost and time required to plan for and set-up the system.
As we can see, planning for and implementing a smart grid solution may be daunting at first, but with the right approach and assistance from Ethernet specialists, it can be greatly simplified and the benefits and savings it provides are well worth the effort.
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