Internet of Things (IoT) devices and technology are increasingly being integrated into smart grids. These devices come with a lot of security vulnerabilities. To combat this, IoT protocols have been extended with security mechanisms. However, these mechanisms introduce extra processing that can lead to additional delay. This additional delay can affect the reliable operation of a smart power system which depends on prompt communication. This paper investigates the real time properties of IoT communication security protocols. We determine the impact of IoT protocols on the real time requirements of smart grid functions (protection, control, and monitoring). We measure how much communication traffic size and delay are added and how it scales. We determine the requirements that must be met by the optimized security protocols. Three IoT communication protocols were considered: CoAP/DTLS, MQTT/TLS, and XMPP/TLS. Results show both latency and overhead increased by a minimum of $3\times$ for each protocol. The increase in delay was below the recommended maximum standard for microgrid monitoring but exceeded the recommended standard for control operations.

物联网（IoT）设备和技术越来越多地集成到智能电网中。这些设备带有很多安全漏洞。为了解决这个问题，物联网协议已经扩展了安全机制。但是，这些机制引入了额外的处理，这可能导致额外的延迟。此额外的延迟可能会影响智能电源系统的可靠运行，这取决于及时的通信。本文研究了物联网通信安全协议的实时属性。我们确定物联网协议对智能电网功能（保护，控制和监视）的实时要求的影响。我们测量增加了多少通信流量和延迟以及它如何扩展。我们确定优化的安全协议必须满足的要求。考虑了三种IoT通信协议：CoAP / DTLS，MQTT / TLS和XMPP / TLS。结果显示，延迟和开销都至少增加了$3\times$每个协议。延迟的增加低于微电网监控的建议最高标准，但超过了控制操作的建议标准。